Subversion Repositories xmatchpro

--This library is free software; you can redistribute it and/or

--modify it under the terms of the GNU Lesser General Public

--License as published by the Free Software Foundation; either

--version 2.1 of the License, or (at your option) any later version.

--This library 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

--Lesser General Public License for more details.

--You should have received a copy of the GNU Lesser General Public

--License along with this library; if not, write to the Free Software

--Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA

-- e_mail : j.l.nunez-yanez@byacom.co.uk

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

--  ENTITY       = MISS_TYPE_CODER    --

--  version      = 1.0                    --

--  last update  = 10/05/01               --

--  author       = Jose Nunez         --

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

-- FUNCTION

-- miss type coder. Converts incoming miss type to a Huffman code word

-- and associated length.

-- PIN LIST

-- MASK        = mask indicatin how many bytes are valid in the search word

-- LITERAL DATA= the 4 bytes of literal data

-- CODE        = output Huffman code (left aligned)

-- LENGTH      = length (number of valid bits) in the output code

library ieee,dzx;

use ieee.std_logic_1164.all;

entity MISS_TYPE_CODER is

port

(

        MASK : in bit_vector(4 downto 0);

        LITERAL_DATA : in bit_vector(31 downto 0);

        CODE : out bit_vector(33 downto 0);

        LENGTH : out bit_vector(5 downto 0)

);

end MISS_TYPE_CODER;

architecture HUFFMAN of MISS_TYPE_CODER is

begin

MISS_TYPE : process(MASK, LITERAL_DATA)

variable BYTE4, BYTE3, BYTE2, BYTE1 : bit_vector(7 downto 0);

begin

BYTE4 := LITERAL_DATA(31 downto 24);

BYTE3 := LITERAL_DATA(23 downto 16);

BYTE2 := LITERAL_DATA(15 downto 8);

BYTE1 := LITERAL_DATA(7 downto 0);

-- generation of miss code

case MASK is

    when "10000" => CODE <= "1" & "000000000000000000000000000000000" ; LENGTH <= "000001";

    when "11000" => CODE <= "001" & BYTE4 & "00000000000000000000000" ; LENGTH <= "001011";

    when "11100" => CODE <= "0001"& BYTE4 & BYTE3 & "00000000000000" ;  LENGTH <= "010100";

    when "11110" => CODE <= "0000" & BYTE4 & BYTE3 & BYTE2 & "000000" ; LENGTH <= "011100";

    when "11111" => CODE <= "01" & BYTE4 & BYTE3 & BYTE2 & BYTE1 ;      LENGTH <= "100010";

    when others => CODE <= "0000000000000000000000000000000000" ; LENGTH <= "000000";

end case;

end process MISS_TYPE;

end HUFFMAN; -- end of architecture