Method performEncode

src/Encoder/Bootstring.js:155–245

* Performs encode on given content following section 6.3 of RFC 3492. * @protected * @param {Chain} content * @return {number[]|string|Uint8Array|Chain|Promise} Encoded content

(content)

   * @return {number[]|string|Uint8Array|Chain|Promise} Encoded content
   */
  performEncode (content) {
    const {
      initialBias,
      initialN,
      tmin,
      tmax,
      caseSensitivity
    } = this.getSettingValues()

    const delimiter = this.getSettingValue('delimiter').getCodePointAt(0)
    const base = this.getSettingValue('digitMapping').getLength()

    // Prepare content
    if (!caseSensitivity) {
      content = content.toLowerCase()
    }

    // Initialize the state
    const input = content.getCodePoints()
    const inputLength = input.length
    let n = initialN
    let bias = initialBias
    let delta = 0

    // Copy basic code points in the input to the output in order
    const output = []
    for (let i = 0; i < input.length; i++) {
      if (this._isBasic(input[i])) {
        output.push(input[i])
      } else if (input[i] < n) {
        throw new InvalidInputError(
          `Unexpected code point at index ${i}, consider changing initial n ` +
          'to include this code point')
      }
    }

    let h = output.length
    const b = output.length
    if (b > 0) {
      output.push(delimiter)
    }

    let m, q, k, t, c
    while (h < inputLength) {
      // Find the next larger non-basic code point >= n
      m = Number.MAX_SAFE_INTEGER
      for (c of input) {
        if (c >= n && c < m && !this._isBasic(c)) {
          m = c
        }
      }

      // Increase delta enough to advance the decoder's <n,i> state to <m,0>,
      // but guard against overflow
      if (m - n > MathUtil.div(Number.MAX_SAFE_INTEGER - delta, h + 1)) {
        throw new InvalidInputError(integerOverflowMessage)
      }
      delta += (m - n) * (h + 1)