HDLbits——Rotate100

verilog代码：

// Build a 100-bit left/right rotator, with synchronous load and left/right enable.
//A rotator shifts-in the shifted-out bit from the other end of the register,
// unlike a shifter that discards the shifted-out bit and shifts in a zero. If enabled,
// a rotator rotates the bits around and does not modify/discard them.

// 移出的一位不会丢弃而是补在空缺的位置，即就是题目中的a rotator要求
// load: Loads shift register with data[99:0] instead of rotating.
// ena[1:0]: Chooses whether and which direction to rotate.
// 2'b01 rotates right by one bit
// 2'b10 rotates left by one bit
// 2'b00 and 2'b11 do not rotate.
// q: The contents of the rotator.
module top_module(
    input clk,
    input load,
    input [1:0] ena,
    input [99:0] data,
    output reg [99:0] q);
    always @(posedge clk)
    begin
        if(load)begin
            q <= data;
        end
        else begin
            case(ena)
                2'b01:      q <= {q[0],q[99:1]};//拼接运算符号{,} ,向右移动1bit
                2'b10:      q <= {q[98:0],q[99]};//向左边移动1bit
                2'b00,2'b11:q <= q; // 保持
            default:
                q<= q; //所有情况考虑完整的情况下，此处可以省略
            endcase
        end
    end
endmodule

RTL原理图：