Subversion Repositories hilbert_transformer

-- functions for resizing vectors with the comma located at the MSB

-- resize_to_msb_trunc realizes a truncation to the new wordsize, if new_size is lower than old size

-- resize_to_msb_trunc realizes a rounding to the new wordsize, if new_size is lower than old size with the use of one additional adder

-- 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 3 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, see <http://www.gnu.org/licenses/>.

-- Package Definition

library ieee;

use ieee.std_logic_1164.all;

use ieee.numeric_std.all;

package resize_tools_pkg is

  -- function declarations

  function resize_to_msb_trunc(

    x : std_logic_vector;

    new_size : integer

  ) return std_logic_vector;

  function resize_to_msb_round(

    x : std_logic_vector;

    new_size : integer

  ) return std_logic_vector;

end resize_tools_pkg;

-- package body

package body resize_tools_pkg is

  -- function implementations

  function resize_to_msb_trunc(

    x : std_logic_vector;

    new_size : integer

  ) return std_logic_vector is

        variable x_res : std_logic_vector(new_size-1 downto 0);

  begin

                if new_size > x'length then

                        x_res(new_size-1 downto new_size-x'length) := x;

                        x_res(new_size-x'length-1 downto 0) := (others => '0');

                elsif x'length >= new_size then

                        x_res := x(x'length-1 downto x'length-new_size);

                end if;

    return x_res;

  end resize_to_msb_trunc;

  function resize_to_msb_round(

    x : std_logic_vector;

    new_size : integer

  ) return std_logic_vector is

        variable x_res : std_logic_vector(new_size-1 downto 0);

  begin

                if x'length = new_size then

                        x_res := x;

                elsif new_size > x'length then

                        x_res(new_size-1 downto new_size-x'length) := x;

                        x_res(new_size-x'length-1 downto 0) := (others => '0');

                elsif x'length > new_size then

                        if x(x'length-new_size-1) = '1' then

                                x_res := std_logic_vector(signed(x(x'length-1 downto x'length-new_size)) + 1);

                        else

                                x_res := x(x'length-1 downto x'length-new_size);

                        end if;

                end if;

    return x_res;

  end resize_to_msb_round;

end resize_tools_pkg;