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

-- Copyright (C) 2005 Arif Endro Nugroho

-- All rights reserved.

-- 

-- Redistribution and use in source and binary forms, with or without

-- modification, are permitted provided that the following conditions

-- are met:

-- 

-- 1. Redistributions of source code must retain the above copyright

--    notice, this list of conditions and the following disclaimer.

-- 2. Redistributions in binary form must reproduce the above copyright

--    notice, this list of conditions and the following disclaimer in the

--    documentation and/or other materials provided with the distribution.

-- 3. The name of Arif Endro Nugroho may not be used to endorse or promote

--    products derived from this software without specific prior written

--    permission.

-- 

-- THIS SOFTWARE IS PROVIDED BY ARIF ENDRO NUGROHO "AS IS" AND ANY EXPRESS

-- OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED

-- WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE

-- DISCLAIMED. IN NO EVENT SHALL ARIF ENDRO NUGROHO BE LIABLE FOR ANY

-- DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL

-- DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS

-- OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)

-- HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,

-- STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN

-- ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE

-- POSSIBILITY OF SUCH DAMAGE.

-- 

-- End Of License.

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

library ieee;

use ieee.std_logic_1164.all;

package xtime_pkg is

  function xtime_2 ( b : std_logic_vector ) return std_logic_vector;

  function xtime_4 ( c : std_logic_vector ) return std_logic_vector;

  function xtime_8 ( d : std_logic_vector ) return std_logic_vector;

end xtime_pkg;

package body xtime_pkg is

  function xtime_2   ( b : std_logic_vector ) return std_logic_vector is

     variable xtime_2_v  : std_logic_vector (07 downto 00) := ( B"0000_0000" );

     begin

        xtime_2_v := (  b(6 downto 4)                     -- 7,6,5

                     & (b(3 downto 2) xor (b(7) & b(7)))  -- 4,3

                     &  b(1)                              -- 2

                     & (b(0) xor b(7))                    -- 1

                     &  b(7));                            -- 0

     return xtime_2_v;

  end xtime_2;

  function xtime_4  ( c : std_logic_vector ) return std_logic_vector is

     variable xtime_4_v : std_logic_vector (07 downto 00) := ( B"0000_0000" );

     begin

        xtime_4_v := (  c(5)                             -- 7

                     &  c(4)                             -- 6

                     & (c(3) xor c(7))                   -- 5

                     & (c(2) xor c(7) xor c(6))          -- 4

                     & (c(1) xor c(6))                   -- 3

                     & (c(0) xor c(7))                   -- 2

                     & (c(7) xor c(6))                   -- 1

                     &  c(6));                           --

     return xtime_4_v;

  end xtime_4;

  function xtime_8  ( d : std_logic_vector ) return std_logic_vector is

     variable xtime_8_v : std_logic_vector (07 downto 00) := ( B"0000_0000" );

     begin

        xtime_8_v := (  d(4)                            -- 7

                     & (d(3) xor d(7))                  -- 6

                     & (d(2) xor d(7) xor d(6))         -- 5

                     & (d(1) xor d(6) xor d(5))         -- 4

                     & (d(0) xor d(7) xor d(5))         -- 3

                     & (d(7) xor d(6))                  -- 2

                     & (d(6) xor d(5))                  -- 1

                     &  d(5));                          -- 0

     return xtime_8_v;

  end xtime_8;

end xtime_pkg;