UTF8 bits stuff.. not entirely sure what the point of this was.

utf8_bits.hh

template <int OCTETS_>
struct utf8_bits_t
{
  enum : int
  {
    OCTETS = OCTETS_,
    OFFSET = 6 * (OCTETS - 1),
  };

  enum : uint32_t
  {
    MASK       = (0xF8u << (4 - OCTETS)) & 0xFFu,
    VALUE_MASK = (~MASK) & 0xFFu,
    NAME       = (MASK << 1) & 0xFFu,
  };

  uint8_t octet(uint32_t code, int nth)
  {
    if (nth == 0) {
      return static_cast<uint8_t>(NAME | ((code >> OFFSET) & VALUE_MASK));
    } else {
      code >>= (OCTETS - 1) - nth;
      code &= UTF8_VAL_MASK_INTERMEDIATE;
      code |= UTF8_NAME_INTERMEDIATE;
      return static_cast<uint8_t>(code);
    }
  }

  constexpr utf8_bits_t() {}
  constexpr uint32_t value_mask() const { return VALUE_MASK; }
  constexpr uint32_t mask() const { return MASK; }
  constexpr uint32_t name() const { return name; }
  constexpr int octets() const { return octets; }
  constexpr int offset() const { return offset; }
};

using utf8_bits_0 = utf8_bits_t<0>;
using utf8_bits_1 = utf8_bits_t<1>;
using utf8_bits_2 = utf8_bits_t<2>;
using utf8_bits_3 = utf8_bits_t<3>;
using utf8_bits_4 = utf8_bits_t<4>;
using utf8_bits_intermediate = utf8_bits_1;