union_bitfield.cpp

#include <iostream>
#include <cinttypes>
#include <limits>

//combining a union with an anonymous bit field we can:
// get a summary value for the entire bit field
// reference bit field members directly from the union
// use an initializer list to set them
//TODO: how to initialize via the bit field members without un-anonymizing it
union bit_funion_t {
  uint8_t all;
  struct {
    uint8_t front:4;
    uint8_t back:4;
  };
};

int main(void) {
  bit_funion_t b{std::numeric_limits<uint8_t>::max()};

  std::cout << "size: " << sizeof(bit_funion_t) << std::endl;
  std::cout << "front bits: " << static_cast<int>(b.front) << std::endl;
  std::cout << "back bits: " << static_cast<int>(b.back) << std::endl;
  std::cout << "all bits: " << static_cast<int>(b.all) << std::endl;
}