Foundation/Memory/Common.inl

/*
 * Copyright(c) Sophist Solutions, Inc. 1990-2025.  All rights reserved
 */
#include <algorithm>
#include <cstring>
 
#include "Stroika/Foundation/Common/Compare.h"
#include "Stroika/Foundation/Debug/Assertions.h"
#include "Stroika/Foundation/Debug/Sanitizer.h"
 
namespace Stroika::Foundation::Memory {
 
    /*
     ********************************************************************************
     ********************************* Memory::NEltsOf ******************************
     ********************************************************************************
     */
    template <typename ARRAY_TYPE, size_t SIZE_OF_ARRAY>
    inline constexpr size_t NEltsOf ([[maybe_unused]] const ARRAY_TYPE (&arr)[SIZE_OF_ARRAY])
    {
        return SIZE_OF_ARRAY;
    }
 
    /*
     ********************************************************************************
     *************************** Memory::CompareBytes *******************************
     ********************************************************************************
     */
    template <>
    constexpr strong_ordering CompareBytes (const uint8_t* lhs, const uint8_t* rhs, size_t count)
    {
        DISABLE_COMPILER_MSC_WARNING_START (5063)
        DISABLE_COMPILER_CLANG_WARNING_START ("clang diagnostic ignored \"-Wconstant-evaluated\"");
        DISABLE_COMPILER_GCC_WARNING_START ("GCC diagnostic ignored \"-Wtautological-compare\"");
        if constexpr (is_constant_evaluated ()) {
            //Require (count == 0 or lhs != nullptr);
            //Require (count == 0 or rhs != nullptr);
            const uint8_t* li = lhs;
            const uint8_t* ri = rhs;
            for (; count--; ++li, ++ri) {
                if (int cmp = static_cast<int> (*li) - static_cast<int> (*ri)) {
                    return Common::CompareResultNormalizer (cmp);
                }
            }
            return strong_ordering::equal;
        }
        else {
            if (count == 0) {
                return strong_ordering::equal;
            }
            return Common::CompareResultNormalizer (::memcmp (lhs, rhs, count));
        }
        DISABLE_COMPILER_GCC_WARNING_END ("GCC diagnostic ignored \"-Wtautological-compare\"");
        DISABLE_COMPILER_MSC_WARNING_END (5063)
        DISABLE_COMPILER_CLANG_WARNING_END ("clang diagnostic ignored \"-Wconstant-evaluated\"");
    }
    template <typename T>
    constexpr strong_ordering CompareBytes (const T* lhs, const T* rhs, size_t count)
    {
        return CompareBytes (reinterpret_cast<const uint8_t*> (lhs), reinterpret_cast<const uint8_t*> (rhs), count * sizeof (T));
    }
    template <typename TL, size_t EL, typename TR, size_t ER>
    constexpr strong_ordering CompareBytes (span<TL, EL> lhs, span<TR, ER> rhs)
        requires (same_as<remove_cvref_t<TL>, remove_cvref_t<TR>> and is_trivial_v<TL>)
    {
        Require (lhs.size () == rhs.size ());
        return CompareBytes (lhs.data (), rhs.data (), lhs.size ());
    }
 
    /*
     ********************************************************************************
     ******************************** Memory::AsBytes *******************************
     ********************************************************************************
     */
    template <typename T>
    inline span<const byte> AsBytes (const T& elt)
        requires (is_trivial_v<T>)
    {
        return as_bytes (span{&elt, 1}); //return span<const byte>{reinterpret_cast<const byte*> (&elt), sizeof (elt)};
    }
 
    /*
     ********************************************************************************
     ***************************** Memory::ConstSpan ********************************
     ********************************************************************************
     */
    template <class T, size_t EXTENT>
    constexpr span<const T, EXTENT> ConstSpan (span<T, EXTENT> s)
    {
        return s;
    }
 
    /*
     ********************************************************************************
     ***************************** Memory::Intersects *******************************
     ********************************************************************************
     */
    template <typename T1, typename T2, size_t E1, size_t E2>
    constexpr bool Intersects (span<T1, E1> lhs, span<T2, E2> rhs)
    {
        // See Range<T, TRAITS>::Intersects for explanation - avoid direct call here to avoid include file reference
        if (lhs.empty () or rhs.empty ()) {
            return false;
        }
        const byte* lhsStart = addressof (*as_bytes (lhs).data ());
        const byte* rhsStart = addressof (*as_bytes (rhs).data ());
        const byte* lhsEnd   = lhsStart + lhs.size_bytes ();
        const byte* rhsEnd   = rhsStart + rhs.size_bytes ();
        if (rhsEnd <= lhsStart) {
            return false; // combine two cases from Range<T, TRAITS>::Intersects cuz always closed
        }
        if (rhsStart >= lhsEnd) {
            return false; // ""
        }
        return true;
    }
 
    /*
     ********************************************************************************
     ***************************** Memory::SpanBytesCast ****************************
     ********************************************************************************
     */
    template <ISpan TO_SPAN, ISpanBytesCastable<TO_SPAN> FROM_SPAN>
    constexpr TO_SPAN SpanBytesCast (FROM_SPAN src)
    {
        using TO_T = typename TO_SPAN::value_type;
        Require ((src.size_bytes () / sizeof (TO_T)) * sizeof (TO_T) == src.size_bytes ()); // else cannot map evenly
        // allow EITHER size or constness conversions - so NOT re-interpret cast
        TO_SPAN result{(TO_T*)(src.data ()), src.size_bytes () / sizeof (TO_T)}; // no need to worry about overflow cuz then addressses would overflow
        Ensure (src.size_bytes () == result.size_bytes ());                      // size in elements can be <, ==, or >
        return result;
    }
 
    /*
     ********************************************************************************
     ***************************** Memory::CopyBytes ********************************
     ********************************************************************************
     */
    template <Common::trivially_copyable FROM_T, size_t FROM_E, Common::trivially_copyable TO_T, size_t TO_E>
    constexpr span<TO_T, TO_E> CopyBytes (span<FROM_T, FROM_E> src, span<TO_T, TO_E> target) noexcept
        requires (same_as<remove_cv_t<FROM_T>, TO_T>)
    {
        Require (src.size () <= target.size ());
        Require (not Intersects (src, target));
        DISABLE_COMPILER_GCC_WARNING_START ("GCC diagnostic ignored \"-Wstringop-overflow\""); // this suppress doesn't work for g++-11, so must use configure to add suppress to cmdline
        copy (src.begin (), src.end (), target.data ());
        DISABLE_COMPILER_GCC_WARNING_END ("GCC diagnostic ignored \"-Wstringop-overflow\"");
        return target.subspan (0, src.size ());
    }
 
    /*
     ********************************************************************************
     ************************ Memory::CopyOverlappingBytes **************************
     ********************************************************************************
     */
    template <Common::trivially_copyable FROM_T, size_t FROM_E, Common::trivially_copyable TO_T, size_t TO_E>
    constexpr span<TO_T, TO_E> CopyOverlappingBytes (span<FROM_T, FROM_E> src, span<TO_T, TO_E> target) noexcept
        requires (same_as<remove_cv_t<FROM_T>, TO_T>)
    {
        Require (src.size () <= target.size ());
        if (src.size () == 0) {
            Assert (target.size () == 0);
            return target.subspan (0, 0);
        }
        // When copying overlapping ranges, std::copy is appropriate when copying to the left (beginning of the
        // destination range is outside the source range) while std::copy_backward is appropriate when copying
        // to the right (end of the destination range is outside the source range).
        if (Intersects (src, target)) {
            DISABLE_COMPILER_GCC_WARNING_START ("GCC diagnostic ignored \"-Wstringop-overflow\""); // this suppress doesn't work for g++-11, so must use configure to add suppress to cmdline
            span<byte>       targetBytes = as_writable_bytes (target);
            span<const byte> srcBytes    = as_bytes (src);
            if (addressof (*targetBytes.data ()) >= addressof (*srcBytes.data ()) + srcBytes.size ()) {
                // target inside src-range, so copy_backward
                copy_backward (srcBytes.data (), srcBytes.data () + srcBytes.size (), targetBytes.data () + srcBytes.size ());
            }
            else {
                copy (src.begin (), src.end (), target.data ());
            }
            DISABLE_COMPILER_GCC_WARNING_END ("GCC diagnostic ignored \"-Wstringop-overflow\"");
            return target.subspan (0, src.size ());
        }
        else {
            return CopyBytes (src, target);
        }
    }
 
    /*
     ********************************************************************************
     ****************************** Memory::CopySpanData ****************************
     ********************************************************************************
     */
    template <typename FROM_T, size_t FROM_E, typename TO_T, size_t TO_E>
    constexpr span<TO_T, TO_E> CopySpanData (span<FROM_T, FROM_E> src, span<TO_T, TO_E> target)
        requires (not is_const_v<TO_T>)
    {
        Require (not Intersects (src, target));
        Require (src.size () <= target.size ()); // BUT size in BYTES need not match
        if constexpr (Common::trivially_copyable<TO_T> and Common::trivially_copyable<FROM_T> and sizeof (FROM_T) == sizeof (TO_T)) {
            // if elements trivially copyable, and STRIDE of elements same on both sides, can copy as bytes
            return CopyBytes (SpanBytesCast<span<const TO_T, TO_E>> (src), target);
        }
        else {
            // Do a for loop copying each element; this can be used to copy any data,
            // like std::copy, except using spans not iterators, and no warning/error about target assignment (static_cast)
            TO_T* tb = target.data ();
            for (const FROM_T& i : src) {
                *tb++ = static_cast<TO_T> (i);
            }
            return target.subspan (0, src.size ());
        }
    }
 
    /*
     ********************************************************************************
     ********************* Memory::CopyOverlappingSpanData **************************
     ********************************************************************************
     */
    template <typename T, size_t FROM_E, size_t TO_E>
    constexpr span<T, TO_E> CopyOverlappingSpanData (span<T, FROM_E> src, span<T, TO_E> target)
        requires (not is_const_v<T>)
    {
        Require (src.size () == target.size ());
        if (target.size () != 0) {
            if (Intersects (src, target)) {
                // When copying overlapping ranges, std::copy is appropriate when copying to the left (beginning of the
                // destination range is outside the source range) while std::copy_backward is appropriate when copying
                // to the right (end of the destination range is outside the source range).
                if (addressof (*target.data ()) >= addressof (*src.data ())) {
                    // target inside src-range, so copy_backward
                    size_t nItems2Copy = src.size ();
                    copy_backward (src.data (), src.data () + nItems2Copy, target.data () + nItems2Copy);
                }
                else {
                    copy (src.begin (), src.end (), target.data ());
                }
            }
            else {
                return CopySpanData (src, target);
            }
        }
        return target;
    }
 
    /*
     ********************************************************************************
     ********************************* Memory::Insert *******************************
     ********************************************************************************
     */
    template <ISpan INTO_SPAN, ISpan FROM_SPAN>
        requires (same_as<remove_const_t<typename INTO_SPAN::value_type>, remove_const_t<typename FROM_SPAN::value_type>>)
    remove_cvref_t<INTO_SPAN> Insert (const INTO_SPAN& intoLiveSpan, const INTO_SPAN& intoReservedSpan, size_t at, const FROM_SPAN& copyFrom) noexcept
    {
        using T = remove_cvref_t<typename INTO_SPAN::value_type>;
        Require (intoLiveSpan.data () == intoReservedSpan.data () or (intoLiveSpan.size () == 0));
        size_t n2Add = copyFrom.size ();
        Require (intoLiveSpan.size () + copyFrom.size () <= intoReservedSpan.size ());
        Require (at + copyFrom.size () <= intoReservedSpan.size ());
        T* b = intoReservedSpan.data ();
        //
        //                         at          origSize
        //                         v              v
        //      [.....orig data... ...more data...]
        //
        //  becomes (; slide by newS; but last newS elts uninitialized_copy copy, and regular copy rest)
        //
        //                         at      at+n2Add
        //                         v          v
        //      [.....orig data... {copyFrom} ...more data...]
        //
        //
        size_t origSize = intoLiveSpan.size ();
        size_t newSize  = origSize + n2Add;
        Assert (newSize > 0);
 
        // do hack impl based on old array code that seems to work on gcc=14 optimizer
        if constexpr (true) {
            // liven objects at the end so operator= doesn't crash (finds already constructed object to assign over)
            if constexpr (not is_trivially_constructible_v<T>) {
                if constexpr (true) {
                    uninitialized_copy (copyFrom.begin (), copyFrom.end (), b + origSize); // could copy from anywhere todo this or be smarter and copy from right place and do it once, but tricky
                }
                else {
                    for (size_t i = 0; i < n2Add; ++i) {
                        new (b + origSize + i) T{copyFrom[i]};
                    }
                }
            }
 
            // now copy to the right - using INITIALIZED copy
            // must use copy_backward, since if we copied forward we would
            // overwrite values before they got copied
            if constexpr (true) {
                copy_backward (b + at, b + origSize, b + origSize + n2Add);
            }
            else {
                for (size_t i = origSize; i > at; --i) { //
                    b[i - 1 + n2Add] = b[i - 1];
                }
            }
 
            // Then add the 'copyFrom' data
            if constexpr (true) {
                copy (copyFrom.begin (), copyFrom.end (), b + at);
            }
            else {
                for (size_t i = 0; i < n2Add; ++i) {
                    b[at + i] = copyFrom[i];
                }
            }
        }
        else if constexpr (is_trivially_copyable_v<T>) {
            // we don't need to pay attention to what is initialized and what is not so quicker and easier
            // So slosh bytes after at down, and copy in the new ones
            CopyOverlappingBytes (span{b + at, origSize - at}, span{b + at + n2Add, origSize - at});
#if qCompilerAndStdLib_stdlib_ranges_pretty_broken_Buggy
            uninitialized_copy (copyFrom.begin (), copyFrom.end (), b + at);
#else
            ranges::uninitialized_copy (copyFrom, span{b + at, n2Add});
#endif
        }
        else {
            // Simple but not super algorithm, append the data (using uninitialized_copy)
            // and then std::rotate () - idea lifted from MSVC std::vector::insert()
            // reason for trixyness, is cuz we need uninitialized_copy for new stuff (into uninitialized memory)
            // and copy with destruction of old stuff for rest (handled by rotate)
#if qCompilerAndStdLib_stdlib_ranges_pretty_broken_Buggy
            uninitialized_copy (copyFrom.begin (), copyFrom.end (), b + origSize);
#else
            ranges::uninitialized_copy (copyFrom, span{b + origSize, n2Add});
#endif
            rotate (b + at, b + origSize, b + newSize);
        }
        return intoReservedSpan.subspan (0, newSize);
    }
 
    /*
     ********************************************************************************
     ********************************* Memory::Remove *******************************
     ********************************************************************************
     */
    template <ISpan FROM_SPAN>
        requires (not is_const_v<typename FROM_SPAN::value_type>)
    remove_cvref_t<FROM_SPAN> Remove (FROM_SPAN&& spanToEdit, FROM_SPAN&& reservedSpan, size_t from, size_t to) noexcept
    {
        // @todo FIX - this COPIES elements during destroy, but should MOVE THEM - slight performance optimization sometimes
        using T = remove_cvref_t<typename FROM_SPAN::value_type>;
        Require (spanToEdit.data () == reservedSpan.data () or (spanToEdit.data () == nullptr and spanToEdit.size () == 0));
        Require (from <= to);
        Require (to <= spanToEdit.size ());
        T*     b             = reservedSpan.data ();
        size_t amountRemoved = to - from;
 
        // if removing from anything BUT the end of the (live) buffer, we must slide items down
        if (to < spanToEdit.size ()) {
            /*
             * Slide items down. Note - this operates ENTIRELY on LIVE (constructed) objects.
             *      b    b+from       b+to
             *      v      v           v
             *      | .... RANGE2REMOVE|STUFF-AFTER|END-OF-BUFFER
             *  produces
             *      | .....STUFF-AFTER|END-OF-BUFFER
             *                        /\
             *             b+spanToEdit.size()-amountRemoved
             */
            auto copySrcSpan = span{b + to, b + spanToEdit.size ()}; // STUFF-AFTER in first line
            auto copyToSpan  = span{b + from, copySrcSpan.size ()};  // RANGE2REMOVE in first line
            Memory::CopyOverlappingSpanData (copySrcSpan, copyToSpan);
        }
        // but either way, we must destroy a few elements at the end, and return the updated span
        auto destroySpan = span{b + spanToEdit.size () - amountRemoved, amountRemoved};
#if qCompilerAndStdLib_stdlib_ranges_pretty_broken_Buggy
        destroy (destroySpan.begin (), destroySpan.end ());
#else
        ranges::destroy (destroySpan);
#endif
        return reservedSpan.subspan (0, spanToEdit.size () - amountRemoved);
    }
 
    /*
     ********************************************************************************
     ******************************** Memory::OffsetOf ******************************
     ********************************************************************************
     */
    namespace Private_ {
        namespace OffsetOfImpl_ {
            namespace UsingRecursiveSideStruct_ {
                // OffsetOf_ BASED ON CODE FROM - https://gist.github.com/graphitemaster/494f21190bb2c63c5516
#pragma pack(push, 1)
                template <typename MEMBER, size_t N_PAD_BYTES>
                struct Pad {
                    char   pad[N_PAD_BYTES];
                    MEMBER m;
                };
#pragma pack(pop)
                template <typename MEMBER>
                struct Pad<MEMBER, 0> {
                    MEMBER m;
                };
 
                DISABLE_COMPILER_MSC_WARNING_START (4324);
                template <typename BASE, typename MEMBER, size_t O>
                struct MakeUnion {
                    union U {
                        char           c;
                        BASE           base;
                        Pad<MEMBER, O> pad;
                        constexpr U () noexcept
                            : c{} {};
                        ~U () = delete;
                    };
                    //constexpr static U* u{};      // old code did this, but doesn't work if MEMBER field has type which is not allowed to be constexpr --LGP 2023-08-20
                    constexpr static U* u{nullptr}; // don't actually allocate an object (maybe use declval instead?) - cuz else U not literal type sometimes if MEMBER obj type not literal
                };
                DISABLE_COMPILER_MSC_WARNING_END (4324);
 
                template <typename MEMBER, typename BASE_CLASS, typename ORIG_CLASS>
                struct offset_of_impl {
                    template <size_t off, auto union_part = MakeUnion<BASE_CLASS, MEMBER, off>::u>
                    // This gets called with nullptr as 'object' for computing diff below to avoid ever building the object (cuz just computing offsets)
                    Stroika_Foundation_Debug_ATTRIBUTE_NO_SANITIZE_UNDEFINED static constexpr ptrdiff_t offset2 (MEMBER ORIG_CLASS::* member)
                    {
                        if constexpr (off > sizeof (BASE_CLASS)) {
                            throw 1;
                        }
                        else {
                            const auto diff1 = &((static_cast<const ORIG_CLASS*> (&union_part->base))->*member);
                            const auto diff2 = &union_part->pad.m;
                            if (diff1 > diff2) {
                                constexpr auto MIN = (sizeof (MEMBER) < alignof (ORIG_CLASS)) ? sizeof (MEMBER) : alignof (ORIG_CLASS);
                                return offset2<off + MIN> (member);
                            }
                            else {
                                return off;
                            }
                        }
                    }
                };
 
                template <class MEMBER, class BASE_CLASS>
                tuple<MEMBER, BASE_CLASS> get_types (MEMBER BASE_CLASS::*); // never defined, never really called, just used to extract types with decltype()
 
                template <class TheBase = void, class TT>
                inline constexpr size_t offset_of (TT member)
                {
                    using T      = decltype (get_types (declval<TT> ()));
                    using Member = tuple_element_t<0, T>;
                    using Orig   = tuple_element_t<1, T>;
                    using Base   = conditional_t<is_void_v<TheBase>, Orig, TheBase>;
                    return static_cast<size_t> (offset_of_impl<Member, Base, Orig>::template offset2<0> (member));
                }
            }
 
            namespace RequiringDefaultConstructibleObjectType_ {
                // @see https://gist.github.com/graphitemaster/494f21190bb2c63c5516 for more info on maybe how to
                template <typename T1, typename T2>
                struct offset_of {
                    static constexpr size_t offset (T1 T2::* member)
                    {
                        union X {
                            array<char, sizeof (T2)> bytes;
                            T2                       obj;
                            X () {};
                            ~X () {};
                        } objAsUnion;
                        /*
                         * &&& maybe not undefined anymore
                         *  UNDEFINED BEHAVIOR: it is undefined, but for the following reason: expr.add-5.sentence-2
                         * "If the expressions P and Q point to, respectively, elements x[i] and x[j] of 
                         * the same array object x, the expression P - Q has the value i - j; otherwise, the behavior is undefined."]
                         */
                        return size_t (&(objAsUnion.obj.*member)) - size_t (&objAsUnion.obj);
                    }
                };
            }
 
            namespace UsingAlignedByteArrayBuf_ {
                template <typename FIELD_VALUE_TYPE, typename OWNING_OBJECT>
                inline size_t offset_of (FIELD_VALUE_TYPE OWNING_OBJECT::* member)
                {
                    // Still not totally legal for non-std-layout classes, but seems to work, and I haven't found a better way
                    //      --LGP 2021-05-27
                    alignas (OWNING_OBJECT) byte buf[sizeof (OWNING_OBJECT)]{};
                    const OWNING_OBJECT&         o = *reinterpret_cast<const OWNING_OBJECT*> (&buf);
                    auto result = size_t (reinterpret_cast<const char*> (&(o.*member)) - reinterpret_cast<const char*> (&o));
                    // Avoid #include - Ensure (result <= sizeof (OWNING_OBJECT));
                    return result;
                }
            }
 
            namespace UseExplicitDefaultConstructibleStaticInstance_ {
                // @see https://gist.github.com/graphitemaster/494f21190bb2c63c5516 for more info on maybe how to
                // get this working with constexpr and without static object
                template <typename T1, typename T2>
                struct offset_of_ {
                    static inline constexpr T2 sObj_{};
                    static constexpr size_t    offset (T1 T2::* member)
                    {
                        /*
                         *  UNDEFINED BEHAVIOR: it is undefined, but for the following reason: expr.add-5.sentence-2
                         * "If the expressions P and Q point to, respectively, elements x[i] and x[j] of 
                         * the same array object x, the expression P - Q has the value i - j; otherwise, the behavior is undefined."]
                         */
                        return size_t (&(offset_of_<T1, T2>::sObj_.*member)) - size_t (&offset_of_<T1, T2>::sObj_);
                    }
                };
            }
 
            namespace UsingSimpleUnionToConstructActualObj_ {
 
                template <typename OUTER_OBJECT, typename DATA_MEMBER_TYPE>
                inline constexpr size_t offset_of (DATA_MEMBER_TYPE (OUTER_OBJECT::* dataMember))
                {
                    // NOT real assert - just tmphack to test
                    //   auto a1 = Private_::OffsetOfImpl_::UsingRecursiveSideStruct_::offset_of<OUTER_OBJECT> (dataMember);
                    //    auto a2 = PRIVATE_::OffsetOfImpl_::UsingAlignedByteArrayBuf_ (dataMember);
                    //   auto a3 = PRIVATE_::OffsetOfImpl_::RequiringDefaultConstructibleObjectType_::offset_of<DATA_MEMBER_TYPE, OUTER_OBJECT>::offset (dataMember);
                    //WeakAssert (a1 == a2);
 
                    union X {
                        array<char, sizeof (OUTER_OBJECT)> bytes;
                        OUTER_OBJECT                       obj;
                        X () {};
                        ~X () {};
                    } objAsUnion;
 
                    //     auto a4 = size_t (&(objAsUnion.obj.*dataMember)) - size_t (&objAsUnion.bytes);
 
                    /*
                * &&& maybe not undefined anymore
                 *  UNDEFINED BEHAVIOR: it is undefined, but for the following reason: expr.add-5.sentence-2
                 * "If the expressions P and Q point to, respectively, elements x[i] and x[j] of 
                 * the same array object x, the expression P - Q has the value i - j; otherwise, the behavior is undefined."]
                 */
                    return size_t (&(objAsUnion.obj.*dataMember)) - size_t (&objAsUnion.obj);
 
                    //https://stackoverflow.com/questions/12141446/offset-from-member-pointer-without-temporary-instance
                    // return Private_::OffsetOf2_::offset_of<OUTER_OBJECT> (dataMember);
                }
 
            }
        }
    }
 
    template <typename OUTER_OBJECT, typename DATA_MEMBER_TYPE>
    inline constexpr size_t OffsetOf (DATA_MEMBER_TYPE (OUTER_OBJECT::* dataMember))
    {
        //constexpr bool          kTestAllWays_ = false;
        constexpr bool          kTestAllWays_ = true;
        [[maybe_unused]] size_t r1;
        [[maybe_unused]] size_t r2;
        [[maybe_unused]] size_t r3;
        [[maybe_unused]] size_t r4;
        if constexpr (kTestAllWays_) {
            /*
             *  Setup to test/try each implementation. One with apparently best shot of working constexpr is UsingRecursiveSideStruct_
             *  HOWEVER, it requires (on unix) setting -ftemplate-depth=5000 flags, and even then, doesn't really work constexpr (complains about dereferencing nullptr).
             * 
             *  Don't give up, but no success so far. MAYBE works OK/portably without the constexpr stuff. Dunno. Probably NOT for the same deref-nullptr reason.
             */
#if defined(_MSC_VER)
            // Don't bother compiling for gcc/clang cuz fails on some compilers without -fdepth= flag, and no point since wont really work right even
            // if you provide that flag. REVISIT in the future maybe, but for now don't even bother calling
            r1 = Private_::OffsetOfImpl_::UsingRecursiveSideStruct_::offset_of<OUTER_OBJECT> (dataMember);
#endif
            r2 = Private_::OffsetOfImpl_::RequiringDefaultConstructibleObjectType_::offset_of<DATA_MEMBER_TYPE, OUTER_OBJECT>::offset (dataMember);
            r3 = Private_::OffsetOfImpl_::UsingAlignedByteArrayBuf_::offset_of<DATA_MEMBER_TYPE, OUTER_OBJECT> (dataMember);
            if constexpr (is_trivially_default_constructible_v<OUTER_OBJECT>) {
                r4 = Private_::OffsetOfImpl_::UseExplicitDefaultConstructibleStaticInstance_::offset_of_<DATA_MEMBER_TYPE, OUTER_OBJECT>::offset (dataMember);
            }
        }
        size_t r5 = Private_::OffsetOfImpl_::UsingSimpleUnionToConstructActualObj_::offset_of<OUTER_OBJECT, DATA_MEMBER_TYPE> (dataMember);
        size_t rr = r5;
        if (not is_constant_evaluated () and kTestAllWays_) {
#if defined(_MSC_VER)
            Assert (r1 == rr);
#endif
            Assert (r2 == rr);
            Assert (r3 == rr);
            if constexpr (is_trivially_default_constructible_v<OUTER_OBJECT>) {
                Assert (r4 == rr);
            }
        }
        return rr;
    }
 
    /*
     ********************************************************************************
     ********************* Memory::Literals::operator""_b ***************************
     ********************************************************************************
     */
    inline namespace Literals {
        constexpr byte operator""_b (unsigned long long b)
        {
            Require (b <= 0xff);
            return static_cast<byte> (b);
        }
    }
 
    ////////////////////// DEPRECATED .//////////////////////////
    template <typename FIELD_VALUE_TYPE, typename OWNING_OBJECT>
    [[deprecated ("Since Stroika v3.0d2 - just use OffsetOf")]] inline size_t constexpr OffsetOf_Constexpr (FIELD_VALUE_TYPE OWNING_OBJECT::* member)
    {
        return OffsetOf (member);
    }
    template <typename T>
    [[deprecated ("Since Stroika v3.0d12 - use CompareBytes")]] constexpr strong_ordering MemCmp (const T* lhs, const T* rhs, size_t count)
    {
        return CompareBytes (lhs, rhs, count);
    }
    template <typename T>
    [[deprecated ("Since Stroika v3.0d12 - use CompareBytes")]] constexpr strong_ordering MemCmp (span<const T> lhs, span<const T> rhs)
    {
        return CompareBytes (lhs, rhs);
    }
    template <typename T>
    [[deprecated ("Since Stroika v3.0d12 - use CompareBytes")]] constexpr strong_ordering MemCmp (span<T> lhs, span<T> rhs)
    {
        return CompareBytes (lhs, rhs);
    }
    template <typename FROM_T, size_t FROM_E, typename TO_T, size_t TO_E>
    [[deprecated ("Since Stroika v3.0d12 use CopyBytes")]] constexpr span<TO_T, TO_E> CopySpanData_StaticCast (span<const FROM_T, FROM_E> src,
                                                                                                               span<TO_T, TO_E> target)
    {
        return CopySpanData (src, target);
    }
    template <typename FROM_T, size_t FROM_E, typename TO_T, size_t TO_E>
    [[deprecated ("Since Stroika v3.0d12 use CopyBytes")]] constexpr std::span<TO_T, TO_E> CopySpanData_StaticCast (span<FROM_T, FROM_E> src,
                                                                                                                    span<TO_T, TO_E> target)
    {
        return CopySpanData (ConstSpan (src), target);
    }
 
}