-- "blowfishvhdl" is a free synthesizable VHDL Blowfish implementation
-- Copyright (C) 2000  Wesley J. Landaker <wjl@mindless.com>

-- This program is free software; you can redistribute it and/or modify
-- it under the terms of the GNU General Public License as published by
-- the Free Software Foundation; either version 2 of the License, or
-- (at your option) any later version.

-- This program is distributed in the hope that it will be useful,
-- but WITHOUT ANY WARRANTY; without even the implied warranty of
-- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-- GNU General Public License for more details.

-- You should have received a copy of the GNU General Public License
-- along with this program; if not, write to the Free Software
-- Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

-- See http://blowfishvhdl.sourceforge.net for more information.

library ieee;
use ieee.std_logic_1164.all;
use ieee.std_logic_unsigned.all;

entity F is
port (
  clk   : in std_logic;

  sbox0_addr : out std_logic_vector(7 downto 0);
  sbox1_addr : out std_logic_vector(7 downto 0);
  sbox2_addr : out std_logic_vector(7 downto 0);
  sbox3_addr : out std_logic_vector(7 downto 0);

  sbox0_data : in std_logic_vector(31 downto 0);
  sbox1_data : in std_logic_vector(31 downto 0);
  sbox2_data : in std_logic_vector(31 downto 0);
  sbox3_data : in std_logic_vector(31 downto 0);

  xL   : in std_logic_vector(31 downto 0);

  FxL  : out std_logic_vector(31 downto 0)
);
end F;

architecture fishy of F is

signal a : std_logic_vector(7 downto 0);
signal b : std_logic_vector(7 downto 0);
signal c : std_logic_vector(7 downto 0);
signal d : std_logic_vector(7 downto 0);

begin

  -- chunk xL up into bytes
  a <= xL(31 downto 24);
  b <= xL(23 downto 16);
  c <= xL(15 downto 8);
  d <= xL(7 downto 0);

  -- now look these up in the sboxes
  sbox0_addr <= a;
  sbox1_addr <= b;
  sbox2_addr <= c;
  sbox3_addr <= d;

  -- and get the result! (of the last cycle, anyway)
  FxL <= ((sbox0_data + sbox1_data) XOR sbox2_data) + sbox3_data;

end;