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//////////////////////////////////////////////////////////////////////

module

  barrel_shifter

  #(

    parameter W = 32,

    parameter D = W,

    parameter UB = $clog2(D)

  )

  (

    input  direction,       // right = 0, left = 1

    input  op,              // logical = 0, arithmetic = 1; left arithmetic not supported

    input [UB-1:0] amount,  // 0 not allowed

    input [W-1:0] data_in,

    output [W-1:0] data_out,

    input reset,

    input clk

  );

  // --------------------------------------------------------------------

  wire [W-1:0] out [UB:0];

  wire shift_in = direction & op ? data_in[W-1] : 0;

  genvar j, k;

  // --------------------------------------------------------------------

  generate

    for(k = 0; k < D; k = k + 1)

    begin : reversal

      assign out[5][k] = direction ? data_in[k] : data_in[D - 1 - k];

      assign data_out[k] = direction ? out[0][k] : out[0][D - 1 - k];

    end

  endgenerate

  // --------------------------------------------------------------------

  generate

    for(j = 0; j < UB; j = j + 1)

      for(k = 0; k < D; k = k + 1)

      begin : shifter

        if(k > D - 1 - (2**j))

          assign out[j][k] = amount[j] ? shift_in : out[j+1][k];

        else

          assign out[j][k] = amount[j] ? out[j+1][k + (2**j)] : out[j+1][k];

      end

  endgenerate

// --------------------------------------------------------------------

endmodule