--------------------------------------------------------------------------
--------------------------------------------------------------------------
--	File Name 	: bit_types.v
--	File type	: VHDL package description
--	Introduction	: Data types using mcc defined primitives
--	Date Created	: October 22, 1990.
--	
--	Author		: Jayanta Roy
--	Affiliation	: University of Cincinnati,
--			  Department of Computer Engg.
--
--	This document was created as a part of the project funded by
--	the Defense Advanced Research Projects Agency under order no.
--	7056 monitored by the Federal Bureau of Investigation under
--	contract no. J-FBI-89-094 and by the University of Cincinnati
--	Research Council.
--
--	Use of this document is strictly prohibited to those members of
--	the community who do not beleive in sharing their efforts with
--	others. Duplication and distribution is limited to specific
--	request to the author.
--
--		Copyright (C) 1990
--		University of Cincinnati, The Ohio Board of Regents
--		Jayanta Roy and Ranga Vemuri
--		All Rights Reserved
--
--------------------------------------------------------------------------
--------------------------------------------------------------------------

package bit_types is
  type bit_code is ('Z', '0', '1', 'X');
  type bit_code_vector is array (natural range <>) of bit_code;
  function resolve_bit_code(inputs: in bit_code_vector) return bit_code;
  subtype res_MVL is resolve_bit_code bit_code;
  type res_MVL_Vector is array(natural range <>) of res_MVL;
end bit_types;

-- library mcc;
-- use mcc.C_Interface.all;

package body bit_types is
  function resolve_bit_code(inputs: in bit_code_vector)
    return bit_code is
    variable saved_value : bit_code := 'Z';
  begin
    -- for p in inputs'range loop
     -- C_Procedure("printf","input(%d) = %d\n",p,inputs(p));
    -- end loop;
    for i in inputs'range loop
      if inputs(i) = 'X' then
        -- If we ever get an 'X', then the result will be an 'X', 
        -- so go ahead and return.
        return 'X';
      elsif saved_value = 'Z' then
        -- Any value will override a value of 'Z'.  So just save the new value.
        saved_value := inputs(i);
      elsif saved_value /= inputs(i) then
        if inputs(i) /= 'Z' then
        -- There are conflicting values.
          return 'X';
        end if;
      end if;
    end loop;
    return saved_value;
  end;
end bit_types;