wiegand-encoder/lib/encode.js

Encode and decode 26, 34, or 38 bit Wiegand protocol credentials

"use strict";
//
//  src/encode.ts
//  Created by Jesse Youngblood on 02/02/20
//  Copyright (c) 2020 Jesse Youngblood. All rights reserved.
//
var __importDefault = (this && this.__importDefault) || function (mod) {
    return (mod && mod.__esModule) ? mod : { "default": mod };
};
Object.defineProperty(exports, "__esModule", { value: true });
const parity_1 = __importDefault(require("./parity"));
/**
 * Encode a given card number and facility code into a wiegand credential message
 * @param {number} cardNumber - Card number
 * @param {number} facilityCode - Facility code
 * @param {number=16} [cardNumberLength] - How many bits the card number should be
 * @param {number=8} [facilityCodeLength] - How many bits the facility code should be
 * @throws
 * @returns {string} Wiegand credential message
 */
function encode(cardNumber, facilityCode, cardNumberLength = 16, facilityCodeLength = 8) {
    if (Number.isInteger(cardNumber) === false || cardNumber < 0) {
        throw new Error(`Card number must be a positive integer. Received "${cardNumber}"`);
    }
    if (Number.isInteger(facilityCode) === false || facilityCode < 0) {
        throw new Error(`Facility code must be a positive integer. Received "${facilityCode}"`);
    }
    if (Number.isInteger(cardNumberLength) === false || cardNumberLength < 0) {
        throw new Error(`Card number length must be a positive integer. Received "${cardNumberLength}"`);
    }
    if (Number.isInteger(facilityCodeLength) === false || facilityCodeLength < 0) {
        throw new Error(`Facility code length must be a positive integer. Received "${facilityCodeLength}"`);
    }
    // Create binary representations of the card number and facility code
    // Pad the card number to 16 bits, and the facility code to 8 bits
    const cardNumberBinary = cardNumber.toString(2).padStart(cardNumberLength, '0');
    const facilityCodeBinary = facilityCode.toString(2).padStart(facilityCodeLength, '0');
    if (cardNumberBinary.length > cardNumberLength) {
        const max = parseInt(''.padStart(cardNumberLength, '1'), 2);
        throw new Error(`Card number ${cardNumber} is too large to encode in ${cardNumberLength + facilityCodeLength + 2}-bit format. Maximum possible value is ${max}.`);
    }
    if (facilityCodeBinary.length > facilityCodeLength) {
        const max = parseInt(''.padStart(facilityCodeLength, '1'), 2);
        throw new Error(`Facility code ${facilityCode} is too large to encode in ${cardNumberLength + facilityCodeLength + 2}-bit format. Maximum possible value is ${max}.`);
    }
    // Concatenate the binary representations of the facility code and the card number to create the message
    const credential = [facilityCodeBinary, cardNumberBinary].join('');
    // Calculate parity for each half of the message string
    const { left, right } = parity_1.default.calculate(credential);
    // Concatenate the left parity bit, the facility code, the card number, and the right parity bit
    const message = [left, credential, right].join('');
    return message;
}
exports.default = encode;