# woocommerce-pos/1.10.7/vendor_prefixed/chillerlan/php-qrcode/src/Common/GF256.php

WCPOS – Point of Sale (POS) plugin for WooCommerce, version 1.10.7. 361 lines.

- Page: https://pluginprobe.com/plugins/woocommerce-pos/1.10.7/code/vendor_prefixed/chillerlan/php-qrcode/src/Common/GF256.php
- Raw: https://pluginprobe.com/plugins/woocommerce-pos/1.10.7/raw/vendor_prefixed/chillerlan/php-qrcode/src/Common/GF256.php
- Modified: 2026-06-09T13:55:26+00:00

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```php
<?php

/**
 * Class GF256
 *
 * @created      16.01.2021
 * @author       ZXing Authors
 * @author       Smiley <smiley@chillerlan.net>
 * @copyright    2021 Smiley
 * @license      Apache-2.0
 */
namespace WCPOS\Vendor\chillerlan\QRCode\Common;

use WCPOS\Vendor\chillerlan\QRCode\QRCodeException;
use function array_fill;
/**
 * This class contains utility methods for performing mathematical operations over
 * the Galois Fields. Operations use a given primitive polynomial in calculations.
 *
 * Throughout this package, elements of the GF are represented as an int
 * for convenience and speed (but at the cost of memory).
 *
 *
 * @author Sean Owen
 * @author David Olivier
 */
final class GF256
{
    /**
     * irreducible polynomial whose coefficients are represented by the bits of an int,
     * where the least-significant bit represents the constant coefficient
     */
    #	private int $primitive = 0x011D;
    private const logTable = [
        0,
        // the first value is never returned, index starts at 1
        0,
        1,
        25,
        2,
        50,
        26,
        198,
        3,
        223,
        51,
        238,
        27,
        104,
        199,
        75,
        4,
        100,
        224,
        14,
        52,
        141,
        239,
        129,
        28,
        193,
        105,
        248,
        200,
        8,
        76,
        113,
        5,
        138,
        101,
        47,
        225,
        36,
        15,
        33,
        53,
        147,
        142,
        218,
        240,
        18,
        130,
        69,
        29,
        181,
        194,
        125,
        106,
        39,
        249,
        185,
        201,
        154,
        9,
        120,
        77,
        228,
        114,
        166,
        6,
        191,
        139,
        98,
        102,
        221,
        48,
        253,
        226,
        152,
        37,
        179,
        16,
        145,
        34,
        136,
        54,
        208,
        148,
        206,
        143,
        150,
        219,
        189,
        241,
        210,
        19,
        92,
        131,
        56,
        70,
        64,
        30,
        66,
        182,
        163,
        195,
        72,
        126,
        110,
        107,
        58,
        40,
        84,
        250,
        133,
        186,
        61,
        202,
        94,
        155,
        159,
        10,
        21,
        121,
        43,
        78,
        212,
        229,
        172,
        115,
        243,
        167,
        87,
        7,
        112,
        192,
        247,
        140,
        128,
        99,
        13,
        103,
        74,
        222,
        237,
        49,
        197,
        254,
        24,
        227,
        165,
        153,
        119,
        38,
        184,
        180,
        124,
        17,
        68,
        146,
        217,
        35,
        32,
        137,
        46,
        55,
        63,
        209,
        91,
        149,
        188,
        207,
        205,
        144,
        135,
        151,
        178,
        220,
        252,
        190,
        97,
        242,
        86,
        211,
        171,
        20,
        42,
        93,
        158,
        132,
        60,
        57,
        83,
        71,
        109,
        65,
        162,
        31,
        45,
        67,
        216,
        183,
        123,
        164,
        118,
        196,
        23,
        73,
        236,
        127,
        12,
        111,
        246,
        108,
        161,
        59,
        82,
        41,
        157,
        85,
        170,
        251,
        96,
        134,
        177,
        187,
        204,
        62,
        90,
        203,
        89,
        95,
        176,
        156,
        169,
        160,
        81,
        11,
        245,
        22,
        235,
        122,
        117,
        44,
        215,
        79,
        174,
        213,
        233,
        230,
        231,
        173,
        232,
        116,
        214,
        244,
        234,
        168,
        80,
        88,
        175,
    ];
    private const expTable = [1, 2, 4, 8, 16, 32, 64, 128, 29, 58, 116, 232, 205, 135, 19, 38, 76, 152, 45, 90, 180, 117, 234, 201, 143, 3, 6, 12, 24, 48, 96, 192, 157, 39, 78, 156, 37, 74, 148, 53, 106, 212, 181, 119, 238, 193, 159, 35, 70, 140, 5, 10, 20, 40, 80, 160, 93, 186, 105, 210, 185, 111, 222, 161, 95, 190, 97, 194, 153, 47, 94, 188, 101, 202, 137, 15, 30, 60, 120, 240, 253, 231, 211, 187, 107, 214, 177, 127, 254, 225, 223, 163, 91, 182, 113, 226, 217, 175, 67, 134, 17, 34, 68, 136, 13, 26, 52, 104, 208, 189, 103, 206, 129, 31, 62, 124, 248, 237, 199, 147, 59, 118, 236, 197, 151, 51, 102, 204, 133, 23, 46, 92, 184, 109, 218, 169, 79, 158, 33, 66, 132, 21, 42, 84, 168, 77, 154, 41, 82, 164, 85, 170, 73, 146, 57, 114, 228, 213, 183, 115, 230, 209, 191, 99, 198, 145, 63, 126, 252, 229, 215, 179, 123, 246, 241, 255, 227, 219, 171, 75, 150, 49, 98, 196, 149, 55, 110, 220, 165, 87, 174, 65, 130, 25, 50, 100, 200, 141, 7, 14, 28, 56, 112, 224, 221, 167, 83, 166, 81, 162, 89, 178, 121, 242, 249, 239, 195, 155, 43, 86, 172, 69, 138, 9, 18, 36, 72, 144, 61, 122, 244, 245, 247, 243, 251, 235, 203, 139, 11, 22, 44, 88, 176, 125, 250, 233, 207, 131, 27, 54, 108, 216, 173, 71, 142, 1];
    /**
     * Implements both addition and subtraction -- they are the same in GF(size).
     *
     * @return int sum/difference of a and b
     */
    public static function addOrSubtract(int $a, int $b) : int
    {
        return $a ^ $b;
    }
    /**
     * @return GenericGFPoly the monomial representing coefficient * x^degree
     * @throws \chillerlan\QRCode\QRCodeException
     */
    public static function buildMonomial(int $degree, int $coefficient) : GenericGFPoly
    {
        if ($degree < 0) {
            throw new QRCodeException('degree < 0');
        }
        $coefficients = array_fill(0, $degree + 1, 0);
        $coefficients[0] = $coefficient;
        return new GenericGFPoly($coefficients);
    }
    /**
     * @return int 2 to the power of $a in GF(size)
     */
    public static function exp(int $a) : int
    {
        if ($a < 0) {
            $a += 255;
        } elseif ($a >= 256) {
            $a -= 255;
        }
        return self::expTable[$a];
    }
    /**
     * @return int base 2 log of $a in GF(size)
     * @throws \chillerlan\QRCode\QRCodeException
     */
    public static function log(int $a) : int
    {
        if ($a < 1) {
            throw new QRCodeException('$a < 1');
        }
        return self::logTable[$a];
    }
    /**
     * @return int multiplicative inverse of a
     * @throws \chillerlan\QRCode\QRCodeException
     */
    public static function inverse(int $a) : int
    {
        if ($a === 0) {
            throw new QRCodeException('$a === 0');
        }
        return self::expTable[256 - self::logTable[$a] - 1];
    }
    /**
     * @return int product of a and b in GF(size)
     */
    public static function multiply(int $a, int $b) : int
    {
        if ($a === 0 || $b === 0) {
            return 0;
        }
        return self::expTable[(self::logTable[$a] + self::logTable[$b]) % 255];
    }
}

```