Barrel Shifter VHDL Code with diagram to learn

Barrel Shifter: Rotates 8-bit input by a specific amount.

Problem with large input (e.g., 32 bits)
– Large multiplexing structure
– Lengthy code
– Better alternative

Barrel Shifter VHDL Code:
library ieee;
use ieee.std_logic_1164.all;
entity barrel_shifter is
   port(
      a: in std_logic_vector(7 downto 0);
      amt: in std_logic_vector(2 downto 0);
      y: out std_logic_vector(7 downto 0)
   );
end barrel_shifter ;
architecture sel_arch of barrel_shifter is
begin
   with amt select
      y<= a                             when "000",
          a(0) & a(7 downto 1)          when "001",
          a(1 downto 0) & a(7 downto 2) when "010",
          a(2 downto 0) & a(7 downto 3) when "011",
          a(3 downto 0) & a(7 downto 4) when "100",
          a(4 downto 0) & a(7 downto 5) when "101",
          a(5 downto 0) & a(7 downto 6) when "110",
          a(6 downto 0) & a(7) when others; -- 111
end sel_arch;