struct binding for bitwise

int_to_bytes.cpp

#include <cstdint>
#include <iostream>
#include <tuple>
#include <type_traits>

template <typename T>
using unsigned_of = std::conditional_t<
    (sizeof(T) == 1), uint8_t,
    std::conditional_t<(sizeof(T) == 2), uint16_t,
                       std::conditional_t<(sizeof(T) == 4), uint32_t,
                                          std::conditional_t<(sizeof(T) == 8),
                                                             uint64_t, void>>>>;

template <typename Integer>
constexpr auto bytes_of(Integer i) {
  unsigned_of<Integer> value = static_cast<unsigned_of<Integer>>(i);
  if constexpr (sizeof(value) == 1U) {
    return std::tuple<uint8_t>(value);
  } else if constexpr (sizeof(value) == 2U) {
    return std::tuple<uint8_t, uint8_t>(value >> 8U, value & 0x00FF);
  } else if constexpr (sizeof(value) == 4U) {
    return std::tuple<uint8_t, uint8_t, uint8_t, uint8_t>(
        value >> 24U, (value >> 16U) & 0xFF, (value >> 8U) & 0xFF,
        value & 0xFF);
  } else if constexpr (sizeof(value) == 8U) {
    return std::tuple<uint8_t, uint8_t, uint8_t, uint8_t, uint8_t, uint8_t,
                      uint8_t, uint8_t>(
        (value >> 56U) & 0xFF, (value >> 48U) & 0xFF, (value >> 40U) & 0xFF,
        (value >> 32U) & 0xFF, (value >> 24U) & 0xFF, (value >> 16U) & 0xFF,
        (value >> 8U) & 0xFF, value & 0xFF);
  }
}

int main() {
  auto [a, b, c, d] = bytes_of(0x04'03'02'01);

  std::cout << std::hex << static_cast<int>(a) << ',' << static_cast<int>(b)
            << ',' << static_cast<int>(c) << ',' << static_cast<int>(d) << '\n';
}