ads-b/dist/lib/crc24.js

Library for decoding ADS-B messages emitted from Aircraft

'use strict';
Object.defineProperty(exports, "__esModule", { value: true });
var table = [
    0x3935ea,
    0x1c9af5,
    0xf1b77e,
    0x78dbbf,
    0xc397db,
    0x9e31e9,
    0xb0e2f0,
    0x587178,
    0x2c38bc,
    0x161c5e,
    0x0b0e2f,
    0xfa7d13,
    0x82c48d,
    0xbe9842,
    0x5f4c21,
    0xd05c14,
    0x682e0a,
    0x341705,
    0xe5f186,
    0x72f8c3,
    0xc68665,
    0x9cb936,
    0x4e5c9b,
    0xd8d449,
    0x939020,
    0x49c810,
    0x24e408,
    0x127204,
    0x093902,
    0x049c81,
    0xfdb444,
    0x7eda22,
    0x3f6d11,
    0xe04c8c,
    0x702646,
    0x381323,
    0xe3f395,
    0x8e03ce,
    0x4701e7,
    0xdc7af7,
    0x91c77f,
    0xb719bb,
    0xa476d9,
    0xadc168,
    0x56e0b4,
    0x2b705a,
    0x15b82d,
    0xf52612,
    0x7a9309,
    0xc2b380,
    0x6159c0,
    0x30ace0,
    0x185670,
    0x0c2b38,
    0x06159c,
    0x030ace,
    0x018567,
    0xff38b7,
    0x80665f,
    0xbfc92b,
    0xa01e91,
    0xaff54c,
    0x57faa6,
    0x2bfd53,
    0xea04ad,
    0x8af852,
    0x457c29,
    0xdd4410,
    0x6ea208,
    0x375104,
    0x1ba882,
    0x0dd441,
    0xf91024,
    0x7c8812,
    0x3e4409,
    0xe0d800,
    0x706c00,
    0x383600,
    0x1c1b00,
    0x0e0d80,
    0x0706c0,
    0x038360,
    0x01c1b0,
    0x00e0d8,
    0x00706c,
    0x003836,
    0x001c1b,
    0xfff409,
    0x000000,
    0x000000,
    0x000000,
    0x000000,
    0x000000,
    0x000000,
    0x000000,
    0x000000,
    0x000000,
    0x000000,
    0x000000,
    0x000000,
    0x000000,
    0x000000,
    0x000000,
    0x000000,
    0x000000,
    0x000000,
    0x000000,
    0x000000,
    0x000000,
    0x000000,
    0x000000,
    0x000000,
];
var LONG_MSG_BITS = 112;
var SHORT_MSG_BITS = 56;
function hexToBytes(hex) {
    var bytes = [];
    for (var c = 0; c < hex.length; c += 2) {
        bytes.push(parseInt(hex.substr(c, 2), 16));
    }
    return bytes;
}
function crc(hexString) {
    var decimalArray = hexToBytes(hexString);
    var bits = decimalArray.length * 8 === SHORT_MSG_BITS ? SHORT_MSG_BITS : LONG_MSG_BITS;
    var offset = bits === LONG_MSG_BITS ? 0 : LONG_MSG_BITS - SHORT_MSG_BITS;
    var result = 0;
    for (var bitIndex = 0; bitIndex < bits; bitIndex++) {
        var numberIndex = parseInt('' + bitIndex / 8, 10);
        var bit = bitIndex % 8;
        var bitmask = 1 << (7 - bit);
        if (+decimalArray[numberIndex] & bitmask) {
            result ^= table[bitIndex + offset];
        }
    }
    return result.toString(16);
}
exports.crc = crc;