verilog实现lzw压缩算法

LZW压缩算法是一种经典的无损压缩算法，使用字典进行编码和解码，可以有效地减小数据的存储空间。下面是一个简单的Verilog实现LZW压缩算法的示例。

module lzw_compress (
    input clk,
    input rst,
    input [7:0] data_in,
    input valid_in,
    output [15:0] code_out,
    output valid_out
);

// define constants
localparam MAX_DICT_SIZE = 256;
localparam MAX_CODE_WIDTH = 9;
localparam MAX_CODE_VALUE = 512;

// define states
typedef enum logic [2:0] {
    IDLE,
    SEARCH,
    ADD,
    UPDATE
} state_t;

// define signals
reg [7:0] input_char;
reg [7:0] prev_char;
reg [7:0] search_char;
reg [8:0] code_value;
reg [8:0] next_code;
reg [8:0] dict[MAX_DICT_SIZE];
reg [MAX_CODE_WIDTH-1:0] code_width;
state_t state;

// initialize variables
initial begin
    input_char = 0;
    prev_char = 0;
    search_char = 0;
    code_value = 0;
    next_code = 256;
    code_width = 9;
    state = IDLE;
end

// state machine
always @(posedge clk) begin
    if (rst) begin
        input_char <= 0;
        prev_char <= 0;
        search_char <= 0;
        code_value <= 0;
        next_code <= 256;
        code_width <= 9;
        state <= IDLE;
        valid_out <= 0;
        code_out <= 0;
    end else begin
        case (state)
            IDLE: begin
                if (valid_in) begin
                    input_char <= data_in;
                    state <= SEARCH;
                end
            end
            SEARCH: begin
                search_char <= prev_char;
                prev_char <= input_char;
                if (code_value == 0) begin
                    code_value <= input_char;
                    valid_out <= 1;
                    code_out <= input_char;
                    state <= ADD;
                end else if (dict[code_value] == 0) begin
                    dict[code_value] <= next_code;
                    next_code <= next_code + 1;
                    valid_out <= 1;
                    code_out <= code_value;
                    state <= ADD;
                end else if (dict[code_value] == (code_value << 8) + input_char) begin
                    code_value <= dict[code_value];
                    state <= SEARCH;
                end else begin
                    code_value <= dict[code_value];
                    state <= UPDATE;
                end
            end
            ADD: begin
                if (next_code >= MAX_CODE_VALUE) begin
                    code_width <= code_width + 1;
                end
                prev_char <= input_char;
                code_value <= prev_char;
                state <= SEARCH;
            end
            UPDATE: begin
                valid_out <= 1;
                code_out <= code_value;
                dict[code_value] <= next_code;
                next_code <= next_code + 1;
                code_value <= input_char;
                state <= ADD;
            end
        endcase
    end
end

endmodule

这个Verilog代码实现了一个LZW压缩模块，可以压缩输入的数据流并输出压缩后的代码流。模块使用一个字典来存储已经出现的字符和对应的编码值，每次读取一个字符并检查是否在字典中出现过，如果出现了则更新当前编码值，否则将当前字符加入字典中并输出上一个编码值。输出的代码流是固定长度的，可以根据需要调整最大编码值和代码宽度。