main.cpp

#include <cstddef>
#include <cstdint>
#include <vector>
#include <iostream>


#define ALWAYS_INLINE __attribute__((__always_inline__))

namespace
{

template <size_t dst_offset, size_t head_size, size_t... tail_sizes>
ALWAYS_INLINE void copyTemplateMultiple(const char * __restrict * __restrict src_bases, size_t src_index, char * __restrict dst_base)
{
    __builtin_memcpy(dst_base + dst_offset, src_bases[0] + src_index * head_size, head_size);

    if constexpr (sizeof...(tail_sizes) > 0)
        copyTemplateMultiple<dst_offset + head_size, tail_sizes...>(src_bases + 1, src_index, dst_base);
}


/*template <typename T, size_t shift, size_t head_size, size_t... tail_sizes>
ALWAYS_INLINE void pushMultiple(const char * __restrict * __restrict src_bases, size_t src_index, T & dst)
{
    dst += *reinterpret_cast<>(src_bases[0] + src_index * head_size) << shift;

    if constexpr (sizeof...(tail_sizes) > 0)
        pushMultiple<T, shift + head_size * 8, tail_sizes...>(src_bases + 1, src_index, dst);
}*/

}


template <typename T, size_t... sizes>
ALWAYS_INLINE T packMultiple(const char * __restrict * __restrict src_bases, size_t src_index)
{
    T res{};
    copyTemplateMultiple<0, sizes...>(src_bases, src_index, reinterpret_cast<char *>(&res));
    return res;
}

/*template <typename T, size_t... sizes>
ALWAYS_INLINE T packMultiple(const char * __restrict * __restrict src_bases, size_t src_index)
{
    T res{};
    pushMultiple<T, 0, sizes...>(src_bases, src_index, res);
    return res;
}*/


template uint64_t packMultiple<uint64_t, 1,1,1,1,1,1,1,1>(const char * __restrict * __restrict src_bases, size_t src_index);

template uint64_t packMultiple<uint64_t, 2,1,1,1,1,1,1>(const char * __restrict * __restrict src_bases, size_t src_index);
template uint64_t packMultiple<uint64_t, 1,2,1,1,1,1,1>(const char * __restrict * __restrict src_bases, size_t src_index);
template uint64_t packMultiple<uint64_t, 1,1,2,1,1,1,1>(const char * __restrict * __restrict src_bases, size_t src_index);
template uint64_t packMultiple<uint64_t, 1,1,1,2,1,1,1>(const char * __restrict * __restrict src_bases, size_t src_index);
template uint64_t packMultiple<uint64_t, 1,1,1,1,2,1,1>(const char * __restrict * __restrict src_bases, size_t src_index);
template uint64_t packMultiple<uint64_t, 1,1,1,1,1,2,1>(const char * __restrict * __restrict src_bases, size_t src_index);
template uint64_t packMultiple<uint64_t, 1,1,1,1,1,1,2>(const char * __restrict * __restrict src_bases, size_t src_index);

template uint64_t packMultiple<uint64_t, 4,1,1,1,1>(const char * __restrict * __restrict src_bases, size_t src_index);
template uint64_t packMultiple<uint64_t, 1,4,1,1,1>(const char * __restrict * __restrict src_bases, size_t src_index);
template uint64_t packMultiple<uint64_t, 1,1,4,1,1>(const char * __restrict * __restrict src_bases, size_t src_index);
template uint64_t packMultiple<uint64_t, 1,1,1,4,1>(const char * __restrict * __restrict src_bases, size_t src_index);
template uint64_t packMultiple<uint64_t, 1,1,1,1,4>(const char * __restrict * __restrict src_bases, size_t src_index);

template uint64_t packMultiple<uint64_t, 4,2,1,1>(const char * __restrict * __restrict src_bases, size_t src_index);
template uint64_t packMultiple<uint64_t, 4,1,2,1>(const char * __restrict * __restrict src_bases, size_t src_index);
template uint64_t packMultiple<uint64_t, 4,1,1,2>(const char * __restrict * __restrict src_bases, size_t src_index);
template uint64_t packMultiple<uint64_t, 2,4,1,1>(const char * __restrict * __restrict src_bases, size_t src_index);
template uint64_t packMultiple<uint64_t, 1,4,2,1>(const char * __restrict * __restrict src_bases, size_t src_index);
template uint64_t packMultiple<uint64_t, 1,4,1,2>(const char * __restrict * __restrict src_bases, size_t src_index);
template uint64_t packMultiple<uint64_t, 2,1,4,1>(const char * __restrict * __restrict src_bases, size_t src_index);
template uint64_t packMultiple<uint64_t, 1,2,4,1>(const char * __restrict * __restrict src_bases, size_t src_index);
template uint64_t packMultiple<uint64_t, 1,1,4,2>(const char * __restrict * __restrict src_bases, size_t src_index);
template uint64_t packMultiple<uint64_t, 2,1,1,4>(const char * __restrict * __restrict src_bases, size_t src_index);
template uint64_t packMultiple<uint64_t, 1,2,1,4>(const char * __restrict * __restrict src_bases, size_t src_index);
template uint64_t packMultiple<uint64_t, 1,1,2,4>(const char * __restrict * __restrict src_bases, size_t src_index);

template uint64_t packMultiple<uint64_t, 4,2,2>(const char * __restrict * __restrict src_bases, size_t src_index);
template uint64_t packMultiple<uint64_t, 2,4,2>(const char * __restrict * __restrict src_bases, size_t src_index);
template uint64_t packMultiple<uint64_t, 2,2,4>(const char * __restrict * __restrict src_bases, size_t src_index);

template uint64_t packMultiple<uint64_t, 4,4>(const char * __restrict * __restrict src_bases, size_t src_index);

template uint64_t packMultiple<uint64_t, 8>(const char * __restrict * __restrict src_bases, size_t src_index);



int main(int, char **)
{
    size_t size = 100000000;

    std::vector<uint8_t> a(size);
    std::vector<uint32_t> b(size);
    std::vector<uint16_t> c(size);
    std::vector<uint8_t> d(size);

    std::vector<const char *> src(4);
    src[0] = reinterpret_cast<const char *>(a.data());
    src[1] = reinterpret_cast<const char *>(b.data());
    src[2] = reinterpret_cast<const char *>(c.data());
    src[3] = reinterpret_cast<const char *>(d.data());

    std::vector<uint64_t> res(size);

    for (size_t i = 0; i < size; ++i)
    {
        res[i] = packMultiple<uint64_t, sizeof(a[0]), sizeof(b[0]), sizeof(c[0]), sizeof(d[0])>(src.data(), i);
    }

    std::cerr << res[0] << '\n';
    return 0;
}