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--! @file RLshifter.vhd

--! @brief RayTrac Arithmetic Shifter 

--! @author Julián Andrés Guarín Reyes

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-- RAYTRAC

-- Author Julian Andres Guarin

-- RLshifter.vhd

-- This file is part of raytrac.

-- 

--     raytrac 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 3 of the License, or

--     (at your option) any later version.

-- 

--     raytrac 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 raytrac.  If not, see <http://www.gnu.org/licenses/>

library ieee;

use ieee.std_logic_1164.all;

use ieee.std_logic_unsigned.all;

use work.arithpack.all;

entity RLshifter is

        generic (

                shiftFunction   : string  := "SQUARE_ROOT"

                mantissa_width  : integer := 18;

                width                   : integer := 32

        );

        port (

                exp             : in std_logic_vector (integer(ceil(log(real(width),2.0)))-1 downto 0);

                mantis  : in std_logic_vector (mantissa_width-1 downto 0);

                result  : out std_logic_vector (width-1 downto 0)

        );

end RLshifter;

architecture RLshifter_arch of RLshifter is

begin

        leftShift:

        if shiftFunction="SQUARE_ROOT" generate

                sqroot:

                process (mantis, exp)

                        variable expi : integer := conv_integer(exp);

                begin

                        result(width-1 downto expi+1)   <= (others=>'0');

                        result(expi     downto 0)                        <= mantissa(mantissa_width-1 downto mantissa_width-1-exp);

                end sqroot;

        end generate leftShift;

        rightShift:

        if shiftFunction="INVERSION" generate

                inverse:

                process (mantis,exp)

                        variable expi : integer := conv_integer(exp);

                begin

                        if expi>0 then

                                result (width-1 downto width-expi) <= (others =>'0');

                                if expi+mantissa_width<width then

                                        result (width-expi-1 downto width-expi-mantissa_width) <= mantis(mantissa_width-1 downto 0);

                                        result (width-expi-mantissa_width-1 downto 0) <= (others=>'0');

                                else

                                        result (width-expi-1 downto 0) <= mantis(mantissa_width-1 downto mantissa_width+expi-width);

                                end if;

                        else

                                result (width-1 downto width-mantissa_width) <= mantis(mantissa_width-1 downto 0);

                end inverse;

end RLshifter_arch;