@nuintun/qrcode/esm/common/reedsolomon/Encoder.js

A pure JavaScript QRCode encode and decode library.

/**
 * @module QRCode
 * @package @nuintun/qrcode
 * @license MIT
 * @version 5.0.2
 * @author nuintun <nuintun@qq.com>
 * @description A pure JavaScript QRCode encode and decode library.
 * @see https://github.com/nuintun/qrcode#readme
 */

import { Polynomial } from './Polynomial.js';
import { QR_CODE_FIELD_256 } from './GaloisField.js';

/**
 * @module Encoder
 */
function buildGenerator(field, generators, degree) {
  const { length } = generators;
  if (degree >= length) {
    const { generator } = field;
    let lastGenerator = generators[length - 1];
    for (let i = length; i <= degree; i++) {
      const coefficients = new Int32Array([1, field.exp(i - 1 + generator)]);
      const nextGenerator = lastGenerator.multiply(new Polynomial(field, coefficients));
      generators.push(nextGenerator);
      lastGenerator = nextGenerator;
    }
  }
  return generators[degree];
}
class Encoder {
  #field;
  #generators;
  constructor(field = QR_CODE_FIELD_256) {
    this.#field = field;
    this.#generators = [new Polynomial(field, new Int32Array([1]))];
  }
  encode(received, ecLength) {
    const dataBytes = received.length - ecLength;
    const infoCoefficients = new Int32Array(dataBytes);
    const generator = buildGenerator(this.#field, this.#generators, ecLength);
    infoCoefficients.set(received.subarray(0, dataBytes));
    const base = new Polynomial(this.#field, infoCoefficients);
    const info = base.multiplyByMonomial(ecLength, 1);
    const [, remainder] = info.divide(generator);
    const { coefficients } = remainder;
    const numZeroCoefficients = ecLength - coefficients.length;
    const zeroCoefficientsOffset = dataBytes + numZeroCoefficients;
    received.fill(0, dataBytes, zeroCoefficientsOffset);
    received.set(coefficients, zeroCoefficientsOffset);
  }
}

export { Encoder };