--------------------------------------------------------------------------
--
--  bv_images package body.
--
--  Functions that return the string image of values.
--  Each image is a correctly formed literal according to the
--  rules of VHDL-93.
--
--------------------------------------------------------------------------

package body bv_images is


  -- Image of bit vector as binary bit string literal
  -- (in the format B"...")
  -- Length of result is bv'length + 3

  function image (bv : in bit_vector) return string is

    alias bv_norm : bit_vector(1 to bv'length) is bv;
    variable result : string(1 to bv'length + 3);

  begin
    result(1) := 'B';
    result(2) := '"';
    for index in bv_norm'range loop
      if bv_norm(index) = '0' then
        result(index + 2) := '0';
      else
        result(index + 2) := '1';
      end if;
    end loop;
    result(bv'length + 3) := '"';
    return result;
  end image;

  ----------------------------------------------------------------

  -- Image of bit vector as octal bit string literal
  -- (in the format O"...")
  -- Length of result is (bv'length+2)/3 + 3

  function image_octal (bv : in bit_vector) return string is

    constant nr_digits : natural := (bv'length + 2) / 3;
    variable result : string(1 to nr_digits + 3);
    variable bits : bit_vector(0 to 3*nr_digits - 1) := (others => '0');
    variable three_bits : bit_vector(0 to 2);
    variable digit : character;

  begin
    result(1) := 'O';
    result(2) := '"';
    bits(bits'right - bv'length + 1 to bits'right) := bv;
    for index in 0 to nr_digits - 1 loop
      three_bits := bits(3*index to 3*index + 2);
      case three_bits is
	when b"000" =>
	  digit := '0';
	when b"001" =>
	  digit := '1';
	when b"010" =>
	  digit := '2';
	when b"011" =>
	  digit := '3';
	when b"100" =>
	  digit := '4';
	when b"101" =>
	  digit := '5';
	when b"110" =>
	  digit := '6';
	when b"111" =>
	  digit := '7';
	end case;
      result(index + 3) := digit;
    end loop;
    result(nr_digits + 3) := '"';
    return result;
  end image_octal;

  ----------------------------------------------------------------

  -- Image of bit vector as hex bit string literal
  -- (in the format X"...")
  -- Length of result is (bv'length+3)/4 + 3

  function image_hex (bv : in bit_vector) return string is

    constant nr_digits : natural := (bv'length + 3) / 4;
    variable result : string(1 to nr_digits + 3);
    variable bits : bit_vector(0 to 4*nr_digits - 1) := (others => '0');
    variable four_bits : bit_vector(0 to 3);
    variable digit : character;

  begin
    result(1) := 'X';
    result(2) := '"';
    bits(bits'right - bv'length + 1 to bits'right) := bv;
    for index in 0 to nr_digits - 1 loop
      four_bits := bits(4*index to 4*index + 3);
      case four_bits is
	when b"0000" =>
	  digit := '0';
	when b"0001" =>
	  digit := '1';
	when b"0010" =>
	  digit := '2';
	when b"0011" =>
	  digit := '3';
	when b"0100" =>
	  digit := '4';
	when b"0101" =>
	  digit := '5';
	when b"0110" =>
	  digit := '6';
	when b"0111" =>
	  digit := '7';
	when b"1000" =>
	  digit := '8';
	when b"1001" =>
	  digit := '9';
	when b"1010" =>
	  digit := 'A';
	when b"1011" =>
	  digit := 'B';
	when b"1100" =>
	  digit := 'C';
	when b"1101" =>
	  digit := 'D';
	when b"1110" =>
	  digit := 'E';
	when b"1111" =>
	  digit := 'F';
	end case;
      result(index + 3) := digit;
    end loop;
    result(nr_digits + 3) := '"';
    return result;
  end image_hex;


end bv_images;