Method performDecode

src/Encoder/RailFenceCipher.js:90–115

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

(content)

   * @return {number[]|string|Uint8Array|Chain} Decoded content
   */
  performDecode (content) {
    const { key: rows, offset } = this.getSettingValues()
    const length = content.getLength()

    // Cycle after which fence matrix repeats
    const cycle = rows * 2 - 2

    // Create result array of code points
    const result = new Array(length)

    let j = -1
    let x, y

    // Go through virtual matrix rows (y) and cols (x)
    for (y = 0; y < rows; y++) {
      for (x = 0; x < length; x++) {
        // Check if the current x-y-position is situated on the zigzag fence
        if ((y + x + offset) % cycle === 0 || (y - x - offset) % cycle === 0) {
          // Set result for the current x-position
          result[x] = content.getCodePointAt(++j)
        }
      }
    }

    return result
  }
}