RC4.php

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<?php
class PHPExcel_Reader_Excel5_RC4
{
        // Context
        var $s = array();
        var $i = 0;
        var $j = 0;

        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;
        }

        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;
        }
}