Function qrPolynomial

src/qrcode.js:974–1034

(num, shift)

  // ---------------------------------------------------------------------

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

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

    var _this = {}

    _this.getAt = function (index) {
      return _num[index]
    }

    _this.getLength = function () {
      return _num.length
    }

    _this.multiply = function (e) {
      var num = new Array(_this.getLength() + e.getLength() - 1)

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

      return qrPolynomial(num, 0)
    }

    _this.mod = function (e) {
      if (_this.getLength() - e.getLength() < 0) {
        return _this
      }

      var ratio = QRMath.glog(_this.getAt(0)) - QRMath.glog(e.getAt(0))

      var num = new Array(_this.getLength())
      for (var i = 0; i < _this.getLength(); i += 1) {
        num[i] = _this.getAt(i)
      }

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

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