qrcoder/src/qrpolynomial.js

QRCoder is *a pure browser qrcode generation* which is standalone. It is based on a <a href='http://www.d-project.com/qrcode/index.html'>library</a> which build qrcode in various language.

import { QRMath } from './qrmath'

function QRPolynomial (num, shift) {
  if (typeof num.length === 'undefined') {
    throw new Error(num.length + '/' + shift)
  }

  this._num = (function () {
    let offset = 0
    while (offset < num.length && num[offset] === 0) {
      offset += 1
    }
    let _num = new Array(num.length - offset + shift)
    for (let i = 0; i < num.length - offset; i += 1) {
      _num[i] = num[i + offset]
    }
    return _num
  })()
}

QRPolynomial.prototype = {
  getAt: function (index) {
    return this._num[index]
  },
  getLength: function () {
    return this._num.length
  },
  multiply: function (e) {
    const num = new Array(this.getLength() + e.getLength() - 1)
    for (let i = 0; i < this.getLength(); i += 1) {
      for (let j = 0; j < e.getLength(); j += 1) {
        num[i + j] ^= QRMath.gexp(QRMath.glog(this.getAt(i)) + QRMath.glog(e.getAt(j)))
      }
    }

    return new QRPolynomial(num, 0)
  },
  mod: function (e) {
    if (this.getLength() - e.getLength() < 0) {
      return this
    }

    let ratio = QRMath.glog(this.getAt(0)) - QRMath.glog(e.getAt(0))
    const num = new Array(this.getLength())
    for (let i = 0; i < this.getLength(); i += 1) {
      num[i] = this.getAt(i)
    }

    for (let i = 0; i < e.getLength(); i += 1) {
      num[i] ^= QRMath.gexp(QRMath.glog(e.getAt(i)) + ratio)
    }

    // recursive call
    return new QRPolynomial(num, 0).mod(e)
  }
}

export default QRPolynomial