bit_read_BS (Bit_Chain *dat)
{
  const unsigned char two_bit_code = bit_read_BB (dat);
  if (two_bit_code == 0)
    return bit_read_RS (dat);
  else if (two_bit_code == 1)
    return (BITCODE_BS)bit_read_RC (dat) & 0xFF;
  else if (two_bit_code == 2)
    return 0;
  else /* if (two_bit_code == 3) */
    return 256;
}
bit_read_BS (Bit_Chain *dat)
{
  const unsigned char two_bit_code = bit_read_BB (dat);
  if (two_bit_code == 0)
    return bit_read_RS (dat);
  else if (two_bit_code == 1)
    return (BITCODE_BS)bit_read_RC (dat) & 0xFF;
  else if (two_bit_code == 2)
    return 0;
  else  
    return 256;
}