--
-- utility_package.vhd
--
-- Contains useful functions for
-- converting between types.
--
-- Darren Gould
-- Kevin Grant
-- Andrew Stanley-Jones
--
-- EE 552 Project
-- D. Elliott
--


--
-- PACKAGE utility_package
--

library ieee;
	use ieee.std_logic_1164.all;


package utility_package
is	
	function slv_to_natural	(slv: in std_logic_vector) return natural;
end package;


--
-- PACKAGE BODY utility_package
--

library ieee;
	use ieee.std_logic_1164.all;
library work;
	use work.project_package.address_bit_width;


package body utility_package
is
	-- This function converts a vector of
	-- standard logic values into a simple
	-- numerical value.  The vector is
	-- assumed to represent an unsigned
	-- number.  The method for this was
	-- derived from an example in the book
	-- "The Designer's Guide to VHDL"
	-- (Ashenden, 1996) that used bit vectors.
	function slv_to_natural	(slv: in std_logic_vector)
	return natural
	is
	variable result: natural := 0;
	variable a_bit: natural;
	variable bits: bit_vector(slv'range);
	begin
		bits := to_bitvector(slv);
		for i in bits'range loop
			-- this starts at the LSB, virtually
			-- shifting the result to the left
			-- as each bit is added in
			if bits(i) = '1' then
				a_bit := 1;
			else
				a_bit := 0;
			end if;
			result := result + result + a_bit;
		end loop;
		return result;
	end function slv_to_natural;
end package body;