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QR Code Encoder For Java 二维码生成器Java版

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package cn.z.qrcode.encoder;

/**
 * 通用Galois Fields域(通用伽罗华域)
 *
 * 仅适用于QrCode
 *
 * 
 * createDate 2023/05/29 11:11:11
 * 
 *
 * @author ALI[[email protected]]
 * @since 1.0.0
 **/
public class GenericGF {

    /**
     * 维度
     * 256
     */
    private static final int DIMENSION = 256;
    /**
     * 多项式
     * 0x011D -> 0000 0001 0001 1101 -> x^8 + x^4 + x^3 + x^2 + 1
     */
    private static final int POLY = 0x011D;

    /**
     * 指数表
     */
    private static final int[] ExpTable;
    /**
     * 对数表
     */
    private static final int[] LogTable;

    static {
        // 初始化指数表和对数表
        ExpTable = new int[DIMENSION];
        LogTable = new int[DIMENSION];
        int x = 1;
        for (int i = 0; i < DIMENSION; i++) {
            ExpTable[i] = x;
            x <<= 1;
            if (x >= DIMENSION) {
                x ^= POLY;
                x &= DIMENSION - 1;
            }
        }
        for (int i = 0; i < DIMENSION - 1; i++) {
            LogTable[ExpTable[i]] = i;
        }
    }

    private GenericGF() {
    }

    /**
     * 加法
     */
    public static int Addition(int a, int b) {
        return a ^ b;
    }

    /**
     * 2的次方
     */
    public static int Exp(int a) {
        return ExpTable[a];
    }

    /**
     * 逆运算
     */
    public static int Inverse(int a) {
        return ExpTable[DIMENSION - LogTable[a] - 1];
    }

    /**
     * 乘法
     */
    public static int Multiply(int a, int b) {
        if (a == 0 || b == 0) {
            return 0;
        }
        return ExpTable[(LogTable[a] + LogTable[b]) % (DIMENSION - 1)];
    }

}