goog.math.Integer.prototype.multiply = function()

in asdoc/library/closure/goog/math/integer.js [500:556]

• 51 lines of code
• 13 McCabe index (conditional complexity)

goog.math.Integer.prototype.multiply = function(other) {
  if (this.isZero()) {
    return goog.math.Integer.ZERO;
  } else if (other.isZero()) {
    return goog.math.Integer.ZERO;
  }

  if (this.isNegative()) {
    if (other.isNegative()) {
      return this.negate().multiply(other.negate());
    } else {
      return this.negate().multiply(other).negate();
    }
  } else if (other.isNegative()) {
    return this.multiply(other.negate()).negate();
  }

  // If both numbers are small, use float multiplication
  if (this.lessThan(goog.math.Integer.TWO_PWR_24_) &&
      other.lessThan(goog.math.Integer.TWO_PWR_24_)) {
    return goog.math.Integer.fromNumber(this.toNumber() * other.toNumber());
  }

  // Fill in an array of 16-bit products.
  var len = this.bits_.length + other.bits_.length;
  var arr = [];
  for (var i = 0; i < 2 * len; i++) {
    arr[i] = 0;
  }
  for (var i = 0; i < this.bits_.length; i++) {
    for (var j = 0; j < other.bits_.length; j++) {
      var a1 = this.getBits(i) >>> 16;
      var a0 = this.getBits(i) & 0xFFFF;

      var b1 = other.getBits(j) >>> 16;
      var b0 = other.getBits(j) & 0xFFFF;

      arr[2 * i + 2 * j] += a0 * b0;
      goog.math.Integer.carry16_(arr, 2 * i + 2 * j);
      arr[2 * i + 2 * j + 1] += a1 * b0;
      goog.math.Integer.carry16_(arr, 2 * i + 2 * j + 1);
      arr[2 * i + 2 * j + 1] += a0 * b1;
      goog.math.Integer.carry16_(arr, 2 * i + 2 * j + 1);
      arr[2 * i + 2 * j + 2] += a1 * b1;
      goog.math.Integer.carry16_(arr, 2 * i + 2 * j + 2);
    }
  }

  // Combine the 16-bit values into 32-bit values.
  for (var i = 0; i < len; i++) {
    arr[i] = (arr[2 * i + 1] << 16) | arr[2 * i];
  }
  for (var i = len; i < 2 * len; i++) {
    arr[i] = 0;
  }
  return new goog.math.Integer(arr, 0);
};