adapt = function (delta, numPoints, firstTime) {
  var k = 0;
  delta = firstTime ? floor(delta / damp) : delta >> 1;
  delta += floor(delta / numPoints);
  while (delta > baseMinusTMin * tMax >> 1) {
    delta = floor(delta / baseMinusTMin);
    k += base;
  }
  return floor(k + (baseMinusTMin + 1) * delta / (delta + skew));
}
Bias adaptation function as per section 3.4 of RFC 3492.
https://tools.ietf.org/html/rfc3492#section-3.4