<?php
/**
 * Magento
 *
 * NOTICE OF LICENSE
 *
 * This source file is subject to the Open Software License (OSL 3.0)
 * that is bundled with this package in the file LICENSE.txt.
 * It is also available through the world-wide-web at this URL:
 * http://opensource.org/licenses/osl-3.0.php
 * If you did not receive a copy of the license and are unable to
 * obtain it through the world-wide-web, please send an email
 * to license@magento.com so we can send you a copy immediately.
 *
 * DISCLAIMER
 *
 * Do not edit or add to this file if you wish to upgrade Magento to newer
 * versions in the future. If you wish to customize Magento for your
 * needs please refer to http://www.magento.com for more information.
 *
 * @category    Unserialize
 * @package     Unserialize_Reader
 * @copyright  Copyright (c) 2006-2020 Magento, Inc. (http://www.magento.com)
 * @license    http://opensource.org/licenses/osl-3.0.php  Open Software License (OSL 3.0)
 */

/**
 * Class Unserialize_Reader_Str
 */
class Unserialize_Reader_Str
{
    /**
     * @var int|null
     */
    protected $_status = null;

    /**
     * @var int|string
     */
    protected $_length;

    /**
     * @var string
     */
    protected $_value;

    const READING_LENGTH = 1;
    const FINISHED_LENGTH = 2;
    const READING_VALUE = 3;

    /**
     * @param string $char
     * @param string $prevChar
     * @return null|string
     */
    public function read($char, $prevChar)
    {

        if (is_null($this->_status) && $prevChar == Unserialize_Parser::SYMBOL_COLON) {
            $this->_status = self::READING_LENGTH;
        }

        if ($this->_status == self::READING_LENGTH) {
            if ($char != Unserialize_Parser::SYMBOL_COLON) {
                $this->_length .= $char;
            } else {
                $this->_length = (int)$this->_length;
                $this->_status = self::FINISHED_LENGTH;
            }
        }

        if ($this->_status == self::FINISHED_LENGTH) {
            if ($char == Unserialize_Parser::SYMBOL_QUOTE) {
                $this->_status = self::READING_VALUE;
                return null;
            }
        }

        if ($this->_status == self::READING_VALUE) {
            if (strlen($this->_value) < $this->_length) {
                $this->_value .= $char;
                return null;
            }

            if (strlen($this->_value) == $this->_length) {
                if ($char == Unserialize_Parser::SYMBOL_SEMICOLON && $prevChar == Unserialize_Parser::SYMBOL_QUOTE) {
                    return (string)$this->_value;
                }
            }
        }
        return null;
    }
}
