/* test unions and bit fields */

#include <iostream>
#include <iomanip>

using namespace std;

int main()
{

  struct format0{
	unsigned i:16 ;
  };
  struct format1{ // our Gnu C++ appears to do this upside down
	unsigned unused :6;
	unsigned RS:2;
	unsigned I:1;
	unsigned RD:2;
	unsigned OP:5;
  };
  struct format2{
	unsigned ADDR:8;
	unsigned I:1;
	unsigned RD:2;
	unsigned OP:5;
  };
  struct format3{
	int CONST:8;
	unsigned I:1;
	unsigned RD:2;
	unsigned OP:5;
  };

  union instruction{ int i; format0 f0; format1 f1; format2 f2; format3 f3; };

  instruction ins;

  ins.i =0x77F7;

   cout << hex << ins.i <<endl;
   cout << hex << ins.f0.i <<endl;

   cout <<dec;

   cout << ins.f1.OP << " "
	<< ins.f1.RD << " "
	<< ins.f1.I << " "
	<< ins.f1.RS
	 <<endl;

   cout << ins.f2.OP << " "
	<< ins.f2.RD << " "
	<< ins.f2.I << " "
	<< ins.f2.ADDR
	 <<endl;

   cout << ins.f3.OP << " "
	<< ins.f3.RD << " "
	<< ins.f3.I << " "
	<< ins.f3.CONST
	 <<endl;

   ins.f2.OP = 0;
   ins.f2.RD=1;
   ins.f2.I =1;
   ins.f2.ADDR=2;

   cout << ins.f2.OP << " "
	<< ins.f2.RD << " "
	<< ins.f2.I << " "
	<< ins.f2.ADDR
	 <<endl;

   cout << hex << ins.i <<endl;


}