--***************************************************************************
-- pack.vhdl                                                                *
--                     VHDL BIT_VECTOR Operations                           * 
--                                                                          * 
--***************************************************************************
package BIT_FUNCTIONS is

  function SHL0 (v2: BIT_VECTOR; dist: INTEGER) return BIT_VECTOR;
  function SHL1 (v2: BIT_VECTOR; dist: INTEGER) return BIT_VECTOR; 
  function SHL (v2: BIT_VECTOR; fill: BIT) return BIT_VECTOR; 
  function SHR0 (v2: BIT_VECTOR; dist: INTEGER) return BIT_VECTOR; 
  function SHRS (v2: BIT_VECTOR; dist: INTEGER) return BIT_VECTOR; 

  function SHR1 (v2: BIT_VECTOR; dist: INTEGER) return BIT_VECTOR; 
  function SHR (v2: BIT_VECTOR; fill: BIT) return BIT_VECTOR; 

  function INT_TO_BIN (number, length1:integer) return BIT_VECTOR;
  function SIGNED_INT_TO_BIN (number, length1:integer) return BIT_VECTOR;
  function BIN_TO_INT (v2: BIT_VECTOR) return INTEGER;
  function SIGNED_BIN_TO_INT (v2: BIT_VECTOR) return INTEGER;

  function ONES_COMP (v2: BIT_VECTOR) return BIT_VECTOR;
  function TWOs_COMP (v2: BIT_VECTOR) return BIT_VECTOR;
  ---function "-"	(x1, x2: BIT_VECTOR) return BIT_VECTOR;
  function "-"	(x1, x2: BIT_VECTOR) return BIT_VECTOR;
  function DEC(v2: BIT_VECTOR) return BIT_VECTOR;

  function "+"	(x1, x2: BIT_VECTOR) return BIT_VECTOR;
  function INC (v2: BIT_VECTOR) return BIT_VECTOR;

  function ODD_PARITY ( v1 :  BIT_VECTOR ) return BIT;
  function EVEN_PARITY ( v1 :  BIT_VECTOR ) return BIT;

  function REVERSE (v2: BIT_VECTOR) return BIT_VECTOR;
  function SUM(v2 : BIT_VECTOR) return integer;

  function BIT_SLICE (v2: BIT_VECTOR;high_val,low_val:integer)return BIT_VECTOR;
  function ASSIGN_TO_SLICE (v1: BIT_VECTOR; 
                            high_val, low_val: integer;
                            x2: BIT_VECTOR             ) return BIT_VECTOR;
  function "*"  ( x1, x2 :  BIT_VECTOR ) return BIT_VECTOR;

end BIT_FUNCTIONS; 

package body BIT_FUNCTIONS is

--********************************************************************
function SHL0 (v2: BIT_VECTOR; dist: INTEGER) return BIT_VECTOR is
--********************************************************************

   variable v1 : BIT_VECTOR(v2'high downto v2'low);
   variable shift_val: BIT_VECTOR(v1'range);
   variable I: INTEGER;

   begin
      v1 := v2;
      for I in v1'high downto (v1'low + dist) loop
         shift_val(I) := v1(I - dist);
      end loop;

      for I in (v1'low + dist - 1) downto v1'low loop
         shift_val(I) := '0';
      end loop;

      return shift_val;
end SHL0;

--********************************************************************
function SHL1 (v2: BIT_VECTOR; dist: INTEGER) return BIT_VECTOR is
--********************************************************************

   variable v1 : BIT_VECTOR(v2'high downto v2'low);
   variable shift_val: BIT_VECTOR(v1'range);
   variable I: INTEGER;

   begin
      v1 := v2;
      for I in v1'high downto (v1'low + dist) loop
         shift_val(I) := v1(I - dist);
      end loop;

      for I in (v1'low + dist - 1) downto v1'low loop
         shift_val(I) := '1';
      end loop;
   
      return shift_val;
end SHL1;

--********************************************************************
function SHL (v2: BIT_VECTOR; fill: BIT) return BIT_VECTOR is
--********************************************************************

   variable v1 : BIT_VECTOR(v2'high downto v2'low);
   variable shift_val: BIT_VECTOR(v1'range);
   variable I : integer;

   begin
      v1 := v2;
      for I in v1'high downto (v1'low + 1) loop
         shift_val(I) := v1(I - 1);
      end loop;

      shift_val(v1'low) := fill;
      return shift_val;
end SHL;

--********************************************************************
function SHR0 (v2: BIT_VECTOR; dist: INTEGER) return BIT_VECTOR is
--********************************************************************

   variable v1 : BIT_VECTOR(v2'high downto v2'low);
   variable shift_val: BIT_VECTOR(v1'range);
   variable I: INTEGER;

   begin
      v1 := v2;
      for I in v1'low to (v1'high - dist) loop
          shift_val(I) := v1(I + dist);
      end loop;

      for I in (v1'high - dist + 1 ) to v1'high loop
          shift_val(I) := '0';
      end loop;

      return shift_val;
end SHR0;

--********************************************************************
function SHRS (v2: BIT_VECTOR; dist: INTEGER) return BIT_VECTOR is
--********************************************************************

   variable v1 : BIT_VECTOR(v2'high downto v2'low);
   variable shift_val: BIT_VECTOR(v1'range);
   variable I: INTEGER;

   begin
      v1 := v2;
      for I in v1'low to (v1'high - dist -1) loop
          shift_val(I) := v1(I + dist);
      end loop;

      for I in (v1'high - dist ) to (v1'high - 1)  loop
          shift_val(I) := '0';
      end loop;

      shift_val(v1'high) := v1(v1'high);

      return shift_val;

end SHRS;



--********************************************************************
function SHR1 (v2: BIT_VECTOR; dist: INTEGER) return BIT_VECTOR is
--********************************************************************

   variable v1 : BIT_VECTOR(v2'high downto v2'low);
   variable shift_val: BIT_VECTOR(v1'range);
   variable I: INTEGER;

   begin
      v1 := v2;
      for I in v1'low to (v1'high - dist) loop
          shift_val(I) := v1(I + dist);
      end loop;

      for I in (v1'high - dist + 1 ) to v1'high loop
          shift_val(I) := '1';
      end loop;

      return shift_val;
end SHR1;

--********************************************************************
function SHR (v2: BIT_VECTOR; fill: BIT) return BIT_VECTOR is
--********************************************************************

   variable v1 : BIT_VECTOR(v2'high downto v2'low);
   variable shift_val: BIT_VECTOR(v1'range);

   begin
      v1 := v2; 
      for I in v1'low to (v1'high - 1) loop
          shift_val(I) := v1(I + 1);
      end loop;

      shift_val(v1'high) := fill;
      return shift_val;
end SHR;


--********************************************************************
function SIGNED_INT_TO_BIN(Number,Length1 : integer) return BIT_VECTOR is
--********************************************************************

    variable NUM : integer;
    variable temp, temp1 : BIT_VECTOR (length1 - 1 downto 0 ) ;

    begin
      if (Number < 0) then
        NUM := 0 - Number;
      else
        NUM := Number;
      end if;

      temp1 := INT_TO_BIN(NUM, Length1);
      if (Number < 0) then
        temp := twos_comp(temp1);
      else
        temp := temp1;
      end if;

      return temp;
end SIGNED_INT_TO_BIN;


--********************************************************************
function INT_TO_BIN(Number,Length1 : integer) return BIT_VECTOR is
--********************************************************************

    variable temp : BIT_VECTOR (length1 - 1 downto 0 ) ;
    variable NUM, QUOTIENT : integer := 0;

    begin
       QUOTIENT := Number;

       for I in 0 to length1 - 1 loop

          NUM := 0;
          while QUOTIENT > 1 loop
             QUOTIENT:= QUOTIENT-2;
             NUM := NUM + 1;
          end loop;

          case QUOTIENT is
             when 1 => temp(I) := '1';
             when 0 => temp(I) := '0';
             when others => null;
          end case;

          QUOTIENT := NUM;    
       end loop;

      return temp;
end INT_TO_BIN;


--********************************************************************
function SIGNED_BIN_TO_INT (v2: BIT_VECTOR) return integer is
--********************************************************************

   variable v1 : BIT_VECTOR(v2'high downto v2'low);
   variable num : integer;
   variable SUM: integer := 0;

   begin
     if (v2(v2'high) = '1') then
       v1 := twos_comp(v2);
     else
       v1 := v2;
     end if;

     num := BIN_TO_INT(v1);
     if (v2(v2'high) = '1') then
       SUM := 0 - num;
     else
       SUM := num;
     end if;                          

     return SUM;
end SIGNED_BIN_TO_INT;

--********************************************************************
function BIN_TO_INT (v2: BIT_VECTOR) return integer is
--********************************************************************

   variable v1 : BIT_VECTOR(v2'high downto v2'low);
   variable SUM: integer := 0;

   begin
      v1 := v2;
      for N in v1'low to v1'high loop
         if v1(N) = '1' then
            SUM := SUM + (2**(N - v1'low));
         end if;
      end loop;

      return SUM;
end BIN_TO_INT;

--********************************************************************
function ones_comp (v2: BIT_VECTOR) return BIT_VECTOR is
--********************************************************************

   variable v1 : BIT_VECTOR(v2'high downto v2'low);
    variable temp: BIT_VECTOR(v1'range);
    variable I: INTEGER;

   begin
      v1 := v2;
      for I in v1'range loop
         if v1(I) = '0' then
            temp(i) := '1';
         else
            temp(i) := '0';
         end if;
      end loop;

      return temp;
end ones_comp;

--********************************************************************
function twos_comp (v2: BIT_VECTOR) return BIT_VECTOR is
--********************************************************************
 
   variable v1 : BIT_VECTOR(v2'high downto v2'low);
   variable temp: BIT_VECTOR(v1'range);
   variable one_occured : BIT;
   variable N : integer;
 
   begin
      v1 := v2; 

      one_occured := '0';