package bit_pack is
  --功能是把bit_vector轉換成整型
  function vec2int(vec1:bit_vector)
       return integer;
  --功能是把integer轉換為bit_vector類型
  function int2vec(int1,Nbits:integer)
	   return bit_vector;

end bit_pack;

package body bit_pack is

function vec2int(vec1:bit_vector)
       return integer is
variable retval:integer:=0;
alias vec:bit_vector(vec1'length-1 downto 0) is vec1;
begin
  for i in vec'high downto 1 loop
       if (vec(i)='1') then
             retval:=(retval+1)*2;
       else
             retval:=retval*2;
       end if;
  end loop;
  if vec(0)='1' then 
        retval:=retval+1;
  end if;
return retval;
end vec2int;

function int2vec(int1,Nbits:integer)
		return bit_vector is
variable N1:integer;
variable retval:bit_vector(Nbits-1 downto 0);
begin
  assert int1 >=0  
		 report "function int2vec:input integer cannot be negative"
		 severity error;
  N1:=int1;
  for i in retval'reverse_range loop
	  if (N1 mod 2)=1 then
			retval(i):='1';
      else
			retval(i):='0';
      end if;
	  N1:=N1/2;
  end loop;
  return retval;
end int2vec;
end bit_pack;