Method performEncode

src/Encoder/ADFGXCipher.js:111–148

* Performs encode on given content. * @protected * @param {Chain} content * @return {number[]|string|Uint8Array|Chain} Encoded content

(content)

   * @return {number[]|string|Uint8Array|Chain} Encoded content
   */
  async performEncode (content) {
    // Prepare content
    let contentString = content.getString()
    const variantName = this.getSettingValue('variant')
    if (variantName === 'adfgx') {
      // As I and J shares the same alphabet position, replace all J chars
      contentString = contentString.replace(/j/gi, 'i')
    }

    // Derive column map from key
    const key = this.getSettingValue('key')
    const keyLength = key.getLength()
    const columnMap = this.mapElementsToSortedPosition(key.getChars())

    // Encode content to coordinates using Polybius square
    const polybius = await this._polybiusSquare.encode(contentString)
    const polybiusLength = polybius.getLength()

    // Encode Polybius square coordinates using substitution and transposition
    const result = new Array(polybiusLength + keyLength)
    let i, column, row, index
    let j = 0

    for (i = 0; i < keyLength; i++) {
      // Derive column from key
      column = columnMap[i]

      // Go through each column row
      for (row = 0; row * keyLength + column < polybiusLength; row++) {
        // Translate 2D column and row coordintes to 1D index
        index = row * keyLength + column
        result[j++] = polybius.getCodePointAt(index)
      }
    }

    // Group result in pairs of 5 characters each, separated by a space
    return ArrayUtil.joinSlices(ArrayUtil.chunk(result.slice(0, j), 5), [32])
  }

  /**
   * Performs decode on given content.