<?php



namespace PhpOffice\PhpSpreadsheet\Reader\Xls;



class RC4

{

    // Context

    protected $s = [];



    protected $i = 0;



    protected $j = 0;



    /**

     * RC4 stream decryption/encryption constrcutor.

     *

     * @param string $key Encryption key/passphrase

     */

    public function __construct($key)

    {

        $len = strlen($key);



        for ($this->i = 0; $this->i < 256; ++$this->i) {

            $this->s[$this->i] = $this->i;

        }



        $this->j = 0;

        for ($this->i = 0; $this->i < 256; ++$this->i) {

            $this->j = ($this->j + $this->s[$this->i] + ord($key[$this->i % $len])) % 256;

            $t = $this->s[$this->i];

            $this->s[$this->i] = $this->s[$this->j];

            $this->s[$this->j] = $t;

        }

        $this->i = $this->j = 0;

    }



    /**

     * Symmetric decryption/encryption function.

     *

     * @param string $data Data to encrypt/decrypt

     *

     * @return string

     */

    public function RC4($data)

    {

        $len = strlen($data);

        for ($c = 0; $c < $len; ++$c) {

            $this->i = ($this->i + 1) % 256;

            $this->j = ($this->j + $this->s[$this->i]) % 256;

            $t = $this->s[$this->i];

            $this->s[$this->i] = $this->s[$this->j];

            $this->s[$this->j] = $t;



            $t = ($this->s[$this->i] + $this->s[$this->j]) % 256;



            $data[$c] = chr(ord($data[$c]) ^ $this->s[$t]);

        }



        return $data;

    }

}

