Method _adaptBias

src/Encoder/Bootstring.js:360–380

* Bias adaptation function following section 6.1 of RFC 3492. * After each delta is encoded or decoded, bias is set for the next delta. * @param {number} delta * @param {number} numPoints * @param {boolean} firstTime * @return {number}

(delta, numPoints, firstTime)

   * @return {number}
   */
  _adaptBias (delta, numPoints, firstTime) {
    const { digitMapping, tmin, tmax, skew } = this.getSettingValues()
    const base = digitMapping.getLength()

    if (firstTime) {
      const damp = this.getSettingValue('damp')
      delta = MathUtil.div(delta, damp)
    } else {
      delta = MathUtil.div(delta, 2)
    }

    delta += MathUtil.div(delta, numPoints)

    let k = 0
    while (delta > MathUtil.div((base - tmin) * tmax, 2)) {
      delta = MathUtil.div(delta, base - tmin)
      k += base
    }

    return k + MathUtil.div((base - tmin + 1) * delta, delta + skew)
  }

  /**
   * Chooses the next T value based on given parameters.